Version:           1.7.0-1 (using KDE 4.3.4)
OS:                Linux
Installed from:    Debian testing/unstable Packages

I do not remember what I did exactly but I was editing lowpass filter dialog properties. I set cutoff frequency to 0.0001 and hit Ok. After that the UI stopped responding and gdb shows the following deadlock:

(gdb) thread apply all bt full
Thread 2 (Thread 0x7fffe78e8910 (LWP 12673)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:261
No locals.
#1  0x00007ffff4ebca99 in KstWaitCondition::wait (this=0x13fb020, mutex=0x13fb000, time=18446744073709551615) at kstwaitcondition_unix.cpp:313
        ret = 0
#2  0x00007ffff4e8e1fa in KstRWLock::writeLock (this=0x13faff8) at rwlock.cpp:100
        lock = {mtx = 0x13fb000}
        me = 140737078266128
#3  0x00007ffff4b5d48a in KstDataObject::writeLock (this=0x13faf90) at kstdataobject.cpp:323
No locals.
#4  0x00007ffff78ef1a6 in KstWriteLocker (this=0x7fffe78e7b70, l=0x13faff8) at ../../../kst/src/libkst/rwlock.h:78
No locals.
#5  0x00007ffff4ebb7fd in KstPrimitive::update (this=0x12c9ff0, update_counter=22349) at kstprimitive.cpp:58
        pl = {_l = 0x13faff8}
        prov = {ptr = 0x13faf90}
        force = false
        providerRC = KstObject::NO_CHANGE
        rc = 32767
#6  0x00007ffff4b890de in KstVCurve::update (this=0x11d6680, update_counter=22349) at kstvcurve.cpp:236
        force = false
        cxV = {ptr = 0x12c9ff0}
        depUpdated = false
        exV = {ptr = 0x113a020}
        exmV = {ptr = 0x0}
        cyV = {ptr = 0x11f2240}
        eyV = {ptr = 0x0}
        eymV = {ptr = 0x7fffe78e7ca0}
#7  0x00007ffff7a0f9f0 in UpdateThread::doUpdates (this=0xe8e3f0, force=true, gotData=0x7fffe78e7ff2) at updatethread.cpp:212
        bcp = {ptr = 0x11d6680}
        ut = KstObject::NO_CHANGE
        i = 4
        cl = {<QValueList<KstSharedPtr<KstBaseCurve> >> = {sh = 0x7fffe0005160}, _vptr.KstObjectList = 0x7ffff7da9450, _lock = {_vptr.KstRWLock = 0x7ffff50d85b0, _mutex = <incomplete type>, _readerWait = {_vptr.KstWaitCondition = 0x7ffff50da5b0, d = 0x7fffe0008310}, _writerWait = {_vptr.KstWaitCondition = 0x7ffff50da5b0, d = 0x7fffe0008e20}, _readCount = 0, _writeCount = 0, _waitingReaders = 0, _waitingWriters = 0, _writeLocker = 140737345051168, _readLockers = {sh = 0x7fffe0019f50}}}
        dol = {<QValueList<KstSharedPtr<KstDataObject> >> = {sh = 0x7fffe000b270}, _vptr.KstObjectList = 0x7ffff7dba210, _lock = {_vptr.KstRWLock = 0x7ffff50d85b0, _mutex = <incomplete type>, _readerWait = {_vptr.KstWaitCondition = 0x7ffff50da5b0, d = 0x7fffe00157a0}, _writerWait = {_vptr.KstWaitCondition = 0x7ffff50da5b0, d = 0x7fffe0001870}, _readCount = 0, _writeCount = 0, _waitingReaders = 0, _waitingWriters = 0, _writeLocker = 53, _readLockers = {sh = 0x7fffe00daa10}}}
        U = KstObject::UPDATE
        __PRETTY_FUNCTION__ = "bool UpdateThread::doUpdates(bool, bool*)"
#8  0x00007ffff7a0f613 in UpdateThread::run (this=0xe8e3f0) at updatethread.cpp:114
        gotData = false
        force = true
        updateTime = 200
#9  0x00007ffff64ace5b in QThreadInstance::start(void*) () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#10 0x00007ffff3b2273a in start_thread (arg=<value optimized out>) at pthread_create.c:300
        __res = <value optimized out>
        pd = 0x7fffe78e8910
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {140737078266128, -369698354882378577, 140737488344176, 140737078266128, 140737354129472, 3, 369680355303654575, 369706568745256111}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = <value optimized out>
#11 0x00007ffff6ceb69d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
No locals.
#12 0x0000000000000000 in ?? ()
No symbol table info available.

Thread 1 (Thread 0x7ffff7fc9750 (LWP 12668)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:261
No locals.
#1  0x00007ffff4ebca99 in KstWaitCondition::wait (this=0x11f22c0, mutex=0x11f22b0, time=18446744073709551615) at kstwaitcondition_unix.cpp:313
        ret = 0
#2  0x00007ffff4e8dfff in KstRWLock::readLock (this=0x11f22a8) at rwlock.cpp:60
        it = {node = 0x1366260}
        lock = {mtx = 0x11f22b0}
        me = 140737353914192
#3  0x00007ffff79be936 in KstObjectItem::update (this=0x153e120, recursive=true, localUseCount=0) at kstdatamanager_i.cpp:293
        inUse = true
        field = {static null = {static null = <same as static member of an already seen type>, d = 0x628e20, static shared_null = 0x628e20}, d = 0xb8a400, static shared_null = 0x628e20}
        x = {ptr = 0x11f2240}
        __PRETTY_FUNCTION__ = "void KstObjectItem::update(bool, int)"
#4  0x00007ffff79bf461 in KstObjectItem::update (this=0x12bb180, recursive=true, localUseCount=0) at kstdatamanager_i.cpp:367
        oi = 0x153e120
        i = 0x153e170
        found = false
        tn = {static null = {static null = <same as static member of an already seen type>, d = 0x628e20, static shared_null = 0x628e20}, d = 0x1424dc0, static shared_null = 0x628e20}
        p = {node = 0x15edfb0}
        vl = {<QMap<QString, KstSharedPtr<KstVector> >> = {sh = 0xff8600}, _vptr.KstObjectMap = 0x7ffff7dacc30}
        vlEnd = {node = 0x1660c10}
        trash = {<QGList> = {<> = {<No data fields>}, firstNode = 0x0, lastNode = 0x0, curNode = 0x0, curIndex = -1, numNodes = 0, iterators = 0x0}, <No data fields>}
        ml = {<QMap<QString, KstSharedPtr<KstMatrix> >> = {sh = 0xc9b940}, _vptr.KstObjectMap = 0x7ffff7db5050}
        mlEnd = {node = 0x15a4070}
        field = {static null = {static null = <same as static member of an already seen type>, d = 0x628e20, static shared_null = 0x628e20}, d = 0x159f630, static shared_null = 0x628e20}
        inUse = true
        x = {ptr = 0x13faf90}
        __PRETTY_FUNCTION__ = "void KstObjectItem::update(bool, int)"
#5  0x00007ffff79c56a7 in KstDataManagerI::update (this=0x75df40) at kstdatamanager_i.cpp:994
        oi = 0x12bb180
        i = 0x12bb1d0
        dol = {_l = 0x13faff8}
        found = false
        it = {node = 0x1333ed0}
        svl = {<QValueList<KstSharedPtr<KstSVector> >> = {sh = 0x7ffff6bbe8a0}, _vptr.KstObjectList = 0x7fffffffc740, _lock = {_vptr.KstRWLock = 0x7ffff6c1c5a0, _mutex = <incomplete type>, _readerWait = {_vptr.KstWaitCondition = 0x7ffff6bbe8a0, d = 0x7ffff6c1c5a0}, _writerWait = {_vptr.KstWaitCondition = 0xb2ff20, d = 0x0}, _readCount = 15582944, _writeCount = 0, _waitingReaders = 32, _waitingWriters = 0, _writeLocker = 140737332897952, _readLockers = {sh = 0x7ffff6c1c5a0}}}
        avl = {<QValueList<KstSharedPtr<KstAVector> >> = {sh = 0x159cf70}, _vptr.KstObjectList = 0x7ffff6c1c5a0, _lock = {_vptr.KstRWLock = 0x0, _mutex = <incomplete type>, _readerWait = {_vptr.KstWaitCondition = 0x7ffff6bbe8a0, d = 0x7ffff6c1c5a0}, _writerWait = {_vptr.KstWaitCondition = 0x7ffff5ebe160, d = 0x7fffffffc720}, _readCount = -155457376, _writeCount = 32767, _waitingReaders = -155073120, _waitingWriters = 32767, _writeLocker = 15798560, _readLockers = {sh = 0x0}}}
        rml = {<QValueList<KstSharedPtr<KstRMatrix> >> = {sh = 0x0}, _vptr.KstObjectList = 0x7ffff6c1c5a0, _lock = {_vptr.KstRWLock = 0x12, _mutex = <incomplete type>, _readerWait = {_vptr.KstWaitCondition = 0x159d750, d = 0x0}, _writerWait = {_vptr.KstWaitCondition = 0x7fffffffc820, d = 0xed6140}, _readCount = -10640, _writeCount = 32767, _waitingReaders = -155073120, _waitingWriters = 32767, _writeLocker = 0, _readLockers = {sh = 0x12}}}
        currentItem = 0x12465c0
        trash = {<QGList> = {<> = {<No data fields>}, firstNode = 0x0, lastNode = 0x0, curNode = 0x0, curIndex = -1, numNodes = 0, iterators = 0x0}, <No data fields>}
        rvl = {<QValueList<KstSharedPtr<KstRVector> >> = {sh = 0x7ffff6bbe8a0}, _vptr.KstObjectList = 0x18, _lock = {_vptr.KstRWLock = 0x20, _mutex = <incomplete type>, _readerWait = {_vptr.KstWaitCondition = 0x7fffffffc8b0, d = 0x13}, _writerWait = {_vptr.KstWaitCondition = 0x18, d = 0x7ffff6c1c5a0}, _readCount = -13824, _writeCount = 32767, _waitingReaders = 32, _waitingWriters = 0, _writeLocker = 7802112, _readLockers = {sh = 0x30}}}
        sml = {<QValueList<KstSharedPtr<KstSMatrix> >> = {sh = 0x7fffffffc780}, _vptr.KstObjectList = 0x7fffffffc610, _lock = {_vptr.KstRWLock = 0xedbd50, _mutex = <incomplete type>, _readerWait = {_vptr.KstWaitCondition = 0x0, d = 0x12}, _writerWait = {_vptr.KstWaitCondition = 0x7ffff5ebe4a4, d = 0x7ffff6c1c5a0}, _readCount = 17110624, _writeCount = 0, _waitingReaders = 0, _waitingWriters = 0, _writeLocker = 140737488340944, _readLockers = {sh = 0xed8650}}}
        aml = {<QValueList<KstSharedPtr<KstAMatrix> >> = {sh = 0x7ffff5ebe4a4}, _vptr.KstObjectList = 0x12, _lock = {_vptr.KstRWLock = 0x0, _mutex = <incomplete type>, _readerWait = {_vptr.KstWaitCondition = 0x7fffffffc730, d = 0xedc490}, _writerWait = {_vptr.KstWaitCondition = 0x7fffffffd670, d = 0x7ffff6c1c5a0}, _readCount = 0, _writeCount = 0, _waitingReaders = 18, _waitingWriters = 0, _writeLocker = 140737319265444, _readLockers = {sh = 0x7fffffffc610}}}
#6  0x00007ffff7a81ff2 in KstApp::updateDataManager (this=0x69ef20, onlyVisible=true) at kst.cpp:2241
No locals.
#7  0x00007ffff7a81e4c in KstApp::updateDialogs (this=0x69ef20, onlyVisible=true) at kst.cpp:2200
No locals.
#8  0x00007ffff7a85d1f in KstApp::qt_invoke (this=0x69ef20, _id=237, _o=0x7fffffffcdb0) at kst.moc:634
No locals.
#9  0x00007ffff650f5aa in QObject::activate_signal(QConnectionList*, QUObject*) () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#10 0x00007ffff651185a in QObject::activate_signal(int) () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#11 0x00007ffff7a62046 in KstDoc::updateDialogs (this=0x76ea70) at kstdoc.moc:132
No locals.
#12 0x00007ffff7a62343 in KstDoc::qt_emit (this=0x76ea70, _id=3, _o=0x7fffffffcea0) at kstdoc.moc:182
No locals.
#13 0x00007ffff650f64f in QObject::activate_signal(QConnectionList*, QUObject*) () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#14 0x00007ffff681b42d in QSignal::signal(QVariant const&) () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#15 0x00007ffff6528f14 in QSignal::activate() () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#16 0x00007ffff652f468 in QSingleShotTimer::event(QEvent*) () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#17 0x00007ffff64b2725 in QApplication::internalNotify(QObject*, QEvent*) () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#18 0x00007ffff64b34aa in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#19 0x00007ffff5ebe4a4 in KApplication::notify(QObject*, QEvent*) () from /usr/lib/libkdecore.so.4
No symbol table info available.
#20 0x00007ffff64a9023 in QEventLoop::activateTimers() () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#21 0x00007ffff6463abe in QEventLoop::processEvents(unsigned int) () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#22 0x00007ffff64c8fa1 in QEventLoop::enterLoop() () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#23 0x00007ffff64c8e62 in QEventLoop::exec() () from /usr/lib/libqt-mt.so.3
No symbol table info available.
#24 0x000000000041523c in main (argc=1, argv=0x7fffffffe998) at main.cpp:850
        color = {static color_init = true, static globals_init = true, static colormodel = QColor::d32, d = {argb = 1224736768, d8 = {argb = 1224736768, pix = 84 'T', invalid = 82 'R', dirty = 73 'I', direct = 68 'D'}, d32 = {argb = 1224736768, pix = 1145655892}}}
        pngfile = {static null = {static null = <same as static member of an already seen type>, d = 0x628e20, static shared_null = 0x628e20}, d = 0xe98bb0, static shared_null = 0x628e20}
        bCaption = false
        hsList = {sh = 0xe98a30}
        nOK = false
        wizardfile = {static null = {static null = <same as static member of an already seen type>, d = 0x628e20, static shared_null = 0x628e20}, d = 0x752110, static shared_null = 0x628e20}
        psdList = {sh = 0xe989f0}
        eq_i = {node = 0x0}
        printfile = {static null = {static null = <same as static member of an already seen type>, d = 0x628e20, static shared_null = 0x628e20}, d = 0xe97580, static shared_null = 0x628e20}
        print_and_exit = false
        bIcon = false
        kst = 0x69ef20
        ycolList = {sh = 0x6a25b0}
        errorList = {sh = 0xe98a70}
        i_ycol = 32767
        mat_i = {node = 0x0}
        n_y = 0
        bMiniIcon = false
        yEqList = {sh = 0xe989b0}
        hs_string = {node = 0x0}
        showQuickStart = true
        showDataWizard = false
        in = {skip = 1, doskip = 255, doave = 127, dolegend = false, n = -134393856, f = 32767, rate = 6.9533558073488437e-310, len = 0, has_points = false, sep_plots = false, n_plots = -155159992, n_cols = 32767, n_rows = -136394588, VUnits = {static null = {static null = <same as static member of an already seen type>, d = 0x628e20, static shared_null = 0x628e20}, d = 0x628e20, static shared_null = 0x628e20}, RUnits = {static null = {static null = <same as static member of an already seen type>, d = 0x628e20, static shared_null = 0x628e20}, d = 0x628e20, static shared_null = 0x628e20}}
        matrixList = {sh = 0xe98890}
        args = 0x6402f0
        rc = 0
        i_file = 32767
        i_curve = 1
        fullPath = {static null = {static null = <same as static member of an already seen type>, d = 0x628e20, static shared_null = 0x628e20}, d = 0x628e20, static shared_null = 0x628e20}
        aboutData = {mAppName = 0x41e0bb "kst", mProgramName = 0x41e0b7 "Kst", mVersion = 0x41e0b1 "1.7.0", mShortDescription = 0x41e750 "Kst: a data viewing program.", mLicenseKey = 1, mCopyrightStatement = 0x41e0e8 "(c) 2000-2007 Barth Netterfield", mOtherText = 0x0, mHomepageAddress = 0x41e0d3 "http://kst.kde.org/", mBugEmailAddress = 0x41e0bf "submit@bugs.kde.org", mAuthorList = {sh = 0x63eed0}, mCreditList = {sh = 0x63ef30}, mLicenseText = 0x0, d = 0x63ef90}
        app = <incomplete type>
        i_v = 65535
        i_plot = -6080