Version:           2.11.999 (using 4.1.71 (KDE 4.1.71 (KDE 4.2 >= 20081023)), Gentoo)
Compiler:          i686-pc-linux-gnu-gcc
OS:                Linux (i686) release 2.6.26-gentoo-r1

Steps to reproduce:

1) Create a text file (I used cat /dev/urandom)
2) Right click on that text file -> Compress->Gzip compressed tar archive
3) Right click on the archive -> Extract archive here
4) In the "file already exists dialog": Hit suggest new name and then overvwrite all
5) See ark crash with the backtrace below

Note: Not sure if its interesting, but in the background nepomuk is indexing my HDD.

Application: Ark (ark), signal SIGABRT
[Current thread is 0 (LWP 7364)]

Thread 2 (Thread 0xb4b3ab90 (LWP 7366)):
#0  0xffffe424 in __kernel_vsyscall ()
#1  0xb7e24be5 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0xb7e9c3b3 in QMutexPrivate::wait (this=0x818ba80, timeout=-1) at thread/qmutex_unix.cpp:85
#3  0xb7e97356 in QMutex::lock (this=0xb4b3a068) at thread/qmutex.cpp:188
#4  0xb808dae5 in Kerfuffle::Query::waitForResponse (this=0xb4b3a05c) at /var/tmp/portage/kde-base/ark-4.1.71/work/ark-4.1.71/ark/kerfuffle/queries.cpp:44
#5  0xb4b8865f in LibArchiveInterface::copyFiles (this=0x80dcb40, files=@0x80f31bc, destinationDirectory=@0x80f31c0, flags={i = -1263295996})
    at /var/tmp/portage/kde-base/ark-4.1.71/work/ark-4.1.71/ark/plugins/libarchive/libarchivehandler.cpp:259
#6  0xb80892dd in Kerfuffle::ExtractJob::doWork (this=0x80f31a8) at /var/tmp/portage/kde-base/ark-4.1.71/work/ark-4.1.71/ark/kerfuffle/jobs.cpp:150
#7  0xb80898e8 in Kerfuffle::ThreadExecution::run (this=0x817de88) at /var/tmp/portage/kde-base/ark-4.1.71/work/ark-4.1.71/ark/kerfuffle/threading.cpp:39
#8  0xb737b934 in ThreadWeaver::JobRunHelper::runTheJob (this=0xb4b3a2c8, th=0x818ce48, job=0x817de88) at /var/tmp/portage/kde-base/kdelibs-4.1.71/work/kdelibs-4.1.71/threadweaver/Weaver/Job.cpp:106
#9  0xb737bb0b in ThreadWeaver::Job::execute (this=0x817de88, th=0x818ce48) at /var/tmp/portage/kde-base/kdelibs-4.1.71/work/kdelibs-4.1.71/threadweaver/Weaver/Job.cpp:135
#10 0xb737a99d in ThreadWeaver::ThreadRunHelper::run (this=0xb4b3a340, parent=0x818c3a8, th=0x818ce48)
    at /var/tmp/portage/kde-base/kdelibs-4.1.71/work/kdelibs-4.1.71/threadweaver/Weaver/Thread.cpp:95
#11 0xb737ab31 in ThreadWeaver::Thread::run (this=0x818ce48) at /var/tmp/portage/kde-base/kdelibs-4.1.71/work/kdelibs-4.1.71/threadweaver/Weaver/Thread.cpp:142
#12 0xb7e9ca24 in QThreadPrivate::start (arg=0x818ce48) at thread/qthread_unix.cpp:191
#13 0xb7e21160 in start_thread (arg=0xb4b3ab90) at pthread_create.c:297
#14 0xb6621c0e in clone () from /lib/libc.so.6

Thread 1 (Thread 0xb62b5700 (LWP 7364)):
[KCrash Handler]
#6  0xffffe424 in __kernel_vsyscall ()
#7  0xb6580690 in *__GI_raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#8  0xb6581ed8 in *__GI_abort () at abort.c:88
#9  0xb7e9432f in qt_message_output (msgType=QtFatalMsg, 
    buf=0xbf9acd80 "ASSERT failure in QMutex::unlock(): \"A mutex must be unlocked in the same thread that locked it.\", file thread/qmutex.cpp, line 338") at global/qglobal.cpp:2108
#10 0xb7e943ee in qFatal (msg=0xb7fdde2c "ASSERT failure in %s: \"%s\", file %s, line %d") at global/qglobal.cpp:2309
#11 0xb7e94434 in qt_assert_x (where=0xb7fdef64 "QMutex::unlock()", what=0xb7fdef84 "A mutex must be unlocked in the same thread that locked it.", file=0xb7fdef24 "thread/qmutex.cpp", line=338)
    at global/qglobal.cpp:1886
#12 0xb7e970fe in QMutex::unlock (this=0xb4b3a068) at thread/qmutex.cpp:338
#13 0xb808e612 in Kerfuffle::Query::setResponse (this=0xb4b3a05c, response=
      {d = {data = {c = -48 '�', i = -1080365360, u = 3214601936, b = 208, d = -0.026302706427243916, ll = -4640133576479019312, ull = 13806610497230532304, ptr = 0xbf9aeed0, shared = 0xbf9aeed0}, type = 1067118352, is_shared = 0, is_null = 1}, static handler = 0xb71c2ec0}) at /var/tmp/portage/kde-base/ark-4.1.71/work/ark-4.1.71/ark/kerfuffle/queries.cpp:51
#14 0xb808eb1b in Kerfuffle::OverwriteQuery::execute (this=0xb4b3a05c) at /var/tmp/portage/kde-base/ark-4.1.71/work/ark-4.1.71/ark/kerfuffle/queries.cpp:73
#15 0x08056640 in BatchExtract::qt_metacall (this=0x80c2bc0, _c=QMetaObject::InvokeMetaMethod, _id=2, _a=0xbf9af04c)
    at /var/tmp/portage/kde-base/ark-4.1.71/work/ark-4.1.71/ark/app/batchextract.cpp:92
#16 0xb7fa44e1 in QMetaObject::activate (sender=0x80f31a8, from_signal_index=<value optimized out>, to_signal_index=26, argv=0xbf9af04c) at kernel/qobject.cpp:3028
#17 0xb7fa63d8 in QMetaObject::activate (sender=0x80f31a8, m=0xb8091180, local_signal_index=0, argv=0xbf9af04c) at kernel/qobject.cpp:3098
#18 0xb80817b5 in Kerfuffle::Job::userQuery (this=0x80f31a8, _t1=0xb4b3a05c) at /var/tmp/portage/kde-base/ark-4.1.71/work/ark_build/ark/kerfuffle/moc_jobs.cpp:87
#19 0xb808188c in Kerfuffle::Job::qt_metacall (this=0x80f31a8, _c=QMetaObject::InvokeMetaMethod, _id=0, _a=0x80da200)
    at /var/tmp/portage/kde-base/ark-4.1.71/work/ark_build/ark/kerfuffle/moc_jobs.cpp:73
#20 0xb8081930 in Kerfuffle::ExtractJob::qt_metacall (this=0x80f31a8, _c=QMetaObject::InvokeMetaMethod, _id=26, _a=0x80da200)
    at /var/tmp/portage/kde-base/ark-4.1.71/work/ark_build/ark/kerfuffle/moc_jobs.cpp:198
#21 0xb7f9bedd in QMetaCallEvent::placeMetaCall (this=0x8138038, object=0x80f31a8) at kernel/qobject.cpp:535
#22 0xb7f9dba7 in QObject::event (this=0x80f31a8, e=0x8138038) at kernel/qobject.cpp:1152
#23 0xb6a1afab in QApplicationPrivate::notify_helper (this=0x806ce48, receiver=0x80f31a8, e=0x8138038) at kernel/qapplication.cpp:3809
#24 0xb6a21ae5 in QApplication::notify (this=0xbf9af900, receiver=0x80f31a8, e=0x8138038) at kernel/qapplication.cpp:3399
#25 0xb7a51f95 in KApplication::notify (this=0xbf9af900, receiver=0x80f31a8, event=0x8138038) at /var/tmp/portage/kde-base/kdelibs-4.1.71/work/kdelibs-4.1.71/kdeui/kernel/kapplication.cpp:307
#26 0xb7f8db21 in QCoreApplication::notifyInternal (this=0xbf9af900, receiver=0x80f31a8, event=0x8138038) at kernel/qcoreapplication.cpp:593
#27 0xb7f8e984 in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x80604a8) at kernel/qcoreapplication.h:215
#28 0xb7f8ebc3 in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1097
#29 0xb6ab05a1 in QEventDispatcherX11::processEvents (this=0x806cc58, flags={i = -1080363112}) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:220
#30 0xb7f8c6b0 in QEventLoop::processEvents (this=0xbf9af810, flags={i = -1080363048}) at kernel/qeventloop.cpp:149
#31 0xb7f8c852 in QEventLoop::exec (this=0xbf9af810, flags={i = -1080362984}) at kernel/qeventloop.cpp:200
#32 0xb7f8ec6f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:851
#33 0xb6a1ad43 in QApplication::exec () at kernel/qapplication.cpp:3337
#34 0x08052bb7 in main (argc=4, argv=0xbf9afc94) at /var/tmp/portage/kde-base/ark-4.1.71/work/ark-4.1.71/ark/app/main.cpp:198