Version:           1.9.51 (using 4.00.80 (KDE 4.0.80 >= (KDE 4.1 Beta1), Debian packages)
Compiler:          cc
OS:                Linux (x86_64) release 2.6.25-melech

I deleted three new messages in the inbox by pressing Del three times, and pressed the "+" key before the delete operations had completed.

Program: KMail (kmail), signal SIGSEGV
[Thread debugging using libthread_db enabled]
[New Thread 0x7fa34dec3780 (LWP 17915)]
[KCrash handler]
#5  Q3ListViewItem::height (this=0xbf00000000)
    at itemviews/q3listview.cpp:3954
#6  0x00007fa3471f1918 in Q3ListViewItem::itemBelow (
    this=<value optimized out>) at itemviews/q3listview.cpp:3878
#7  0x00007fa34d64c7ec in KMHeaders::findUnread (this=0x90c2f0, 
    aDirNext=true, aStartAt=-1, onlyNew=false, acceptCurrent=false)
    at /tmp/buildd/kde4pim-4.0.80/kmail/kmheaders.cpp:2024
#8  0x00007fa34d64ba60 in KMHeaders::nextUnreadMessage (this=0x90c2f0, 
    acceptCurrent=false)
    at /tmp/buildd/kde4pim-4.0.80/kmail/kmheaders.cpp:2081
#9  0x00007fa34d8ab702 in KMMainWidget::slotNextUnreadMessage (this=0x90f260)
    at /tmp/buildd/kde4pim-4.0.80/kmail/kmmainwidget.cpp:2427
#10 0x00007fa34d8cdfdd in KMMainWidget::qt_metacall (this=0x90f260, 
    _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, 
    _a=0x7fff56005a20)
    at /tmp/buildd/kde4pim-4.0.80/obj-x86_64-linux-gnu/kmail/kmmainwidget.moc:433
#11 0x00007fa34c789cd6 in QMetaObject::activate (sender=0xaabb70, 
    from_signal_index=<value optimized out>, to_signal_index=6, argv=0x0)
    at kernel/qobject.cpp:3010
#12 0x00007fa34bcaff37 in QAction::triggered (this=0xbf00000000, _t1=false)
    at .moc/release-shared/moc_qaction.cpp:216
#13 0x00007fa34bcb0740 in QAction::activate (this=0xaabb70, 
    event=<value optimized out>) at kernel/qaction.cpp:1119
#14 0x00007fa34bcb218e in QAction::event (this=0xbf00000000, 
    e=<value optimized out>) at kernel/qaction.cpp:1038
#15 0x00007fa34bd09d43 in QWidgetAction::event (this=0xaabb70, 
    event=0x7fff56005f00) at kernel/qwidgetaction.cpp:239
#16 0x00007fa34bcb64df in QApplicationPrivate::notify_helper (this=0x62e700, 
    receiver=0xaabb70, e=0x7fff56005f00) at kernel/qapplication.cpp:3772
#17 0x00007fa34bcbb0b5 in QApplication::notify (this=0x7fff56007400, 
    receiver=0xaabb70, e=0x7fff56005f00) at kernel/qapplication.cpp:3739
#18 0x00007fa34d0edd2b in KApplication::notify (this=0x7fff56007400, 
    receiver=0xaabb70, event=0x7fff56005f00)
    at /tmp/buildd/kde4libs-4.0.80/kdeui/kernel/kapplication.cpp:311
#19 0x00007fa34c775bd9 in QCoreApplication::notifyInternal (
    this=0x7fff56007400, receiver=0xaabb70, event=0x7fff56005f00)
    at kernel/qcoreapplication.cpp:587
#20 0x00007fa34bce9fdc in QShortcutMap::dispatchEvent (
    this=<value optimized out>, e=0x7fff560063d0)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#21 0x00007fa34bceb044 in QShortcutMap::tryShortcutEvent (this=0x62e810, 
    w=<value optimized out>, e=0x7fff560063d0) at kernel/qshortcutmap.cpp:365
#22 0x00007fa34bcbc046 in QApplication::notify (this=0x7fff56007400, 
    receiver=0x90c2f0, e=0x7fff560063d0) at kernel/qapplication.cpp:3403
#23 0x00007fa34d0edd2b in KApplication::notify (this=0x7fff56007400, 
    receiver=0x90c2f0, event=0x7fff560063d0)
    at /tmp/buildd/kde4libs-4.0.80/kdeui/kernel/kapplication.cpp:311
#24 0x00007fa34c775bd9 in QCoreApplication::notifyInternal (
    this=0x7fff56007400, receiver=0x90c2f0, event=0x7fff560063d0)
    at kernel/qcoreapplication.cpp:587
#25 0x00007fa34bd0cb3c in qt_sendSpontaneousEvent (receiver=0x0, 
    event=0xd06560)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#26 0x00007fa34bd3bdf4 in QKeyMapper::sendKeyEvent (keyWidget=0x90c2f0, 
    grab=<value optimized out>, type=QEvent::KeyPress, code=43, 
    modifiers=@0x7fff56006910, text=@0x7fff56006900, 
    autorepeat=<value optimized out>, count=1, nativeScanCode=20, 
    nativeVirtualKey=43, nativeModifiers=0) at kernel/qkeymapper_x11.cpp:1656
#27 0x00007fa34bd3dfb5 in QKeyMapperPrivate::translateKeyEvent (
    this=0x7fff560068c0, keyWidget=0x90c2f0, event=0x7fff56006f50, grab=false)
    at kernel/qkeymapper_x11.cpp:1627
#28 0x00007fa34bd19148 in QApplication::x11ProcessEvent (this=0x7fff56007400, 
    event=0x7fff56006f50) at kernel/qapplication_x11.cpp:3148
#29 0x00007fa34bd3f3c3 in x11EventSourceDispatch (s=0x631c90, callback=0, 
    user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:148
#30 0x00007fa344bc50f2 in g_main_context_dispatch ()
   from /usr/lib/libglib-2.0.so.0
#31 0x00007fa344bc8396 in ?? () from /usr/lib/libglib-2.0.so.0
#32 0x00007fa344bc882f in g_main_context_iteration ()
   from /usr/lib/libglib-2.0.so.0
#33 0x00007fa34c79edff in QEventDispatcherGlib::processEvents (this=0x620c80, 
    flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:325
#34 0x00007fa34bd3f20f in QGuiEventDispatcherGlib::processEvents (
    this=0xbf00000000, flags=<value optimized out>)
    at kernel/qguieventdispatcher_glib.cpp:204
#35 0x00007fa34c775055 in QEventLoop::processEvents (
    this=<value optimized out>, flags=@0x7fff56007220)
    at kernel/qeventloop.cpp:149
#36 0x00007fa34c7751ab in QEventLoop::exec (this=0x7fff56007260, 
    flags=@0x7fff56007270) at kernel/qeventloop.cpp:200
#37 0x00007fa34c7771f9 in QCoreApplication::exec ()
    at kernel/qcoreapplication.cpp:845
#38 0x0000000000402d7a in main (argc=<value optimized out>, 
    argv=<value optimized out>)
    at /tmp/buildd/kde4pim-4.0.80/kmail/main.cpp:130
#0  0x00007fa34b31a210 in __nanosleep_nocancel () from /lib/libc.so.6