Version:           1.7 (using KDE 3.3.0, compiled sources)
Compiler:          gcc version 3.2.3
OS:                Linux (i686) release 2.6.7

How to reproduce:
Select a folder with a large number of mails (e.g. sent mails - I have > 13000 mails there), select a filter (probably not needed, but I did it this way).
Select some mails (~5) and start to move them to another folder and (important!) when you release the mouse button, immediately click it again (being still above the target folder in the folder tree).
Then you always get a SEGFAULT with the following bt (I tried from within gdb):
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 16384 (LWP 19760)]
0x40345dc6 in KMMoveCommand::execute (this=0x8b82408) at qvaluelist.h:525
525         iterator append( const T& x ) { detach(); return sh->insert( end(), x ); }
(gdb) bt
#0  0x40345dc6 in KMMoveCommand::execute (this=0x8b82408) at qvaluelist.h:525
#1  0x4033ddd1 in KMCommand::slotPostTransfer (this=0x8b82408, result=OK) at kmcommands.cpp:199
#2  0x40337d62 in KMCommand::qt_invoke (this=0x8b82408, _id=4, _o=0xbfffec40) at qucom_p.h:312
#3  0x4033b474 in KMMenuCommand::qt_invoke (this=0x8b82408, _id=4, _o=0xbfffec40) at kmcommands.moc:2414
#4  0x4033b820 in KMMoveCommand::qt_invoke (this=0x8b82408, _id=4, _o=0xbfffec40) at kmcommands.moc:2581
#5  0x41af8a11 in QObject::activate_signal (this=0x8b82408, clist=0x8a80028, o=0xbfffec40) at kernel/qobject.cpp:2356
#6  0x40337c07 in KMCommand::messagesTransfered (this=0x8b82408, t0=OK) at kmcommands.moc:120
#7  0x4033e0cd in KMCommand::transferSelectedMsgs (this=0x8b82408) at kmcommands.cpp:289
#8  0x4033dc09 in KMCommand::slotStart (this=0x8b82408) at kmcommands.cpp:191
#9  0x40337d4c in KMCommand::qt_invoke (this=0x8b82408, _id=3, _o=0xbfffee90) at kmcommands.moc:140
#10 0x4033b474 in KMMenuCommand::qt_invoke (this=0x8b82408, _id=3, _o=0xbfffee90) at kmcommands.moc:2414
#11 0x4033b820 in KMMoveCommand::qt_invoke (this=0x8b82408, _id=3, _o=0xbfffee90) at kmcommands.moc:2581
#12 0x41af8a11 in QObject::activate_signal (this=0x84de2a8, clist=0x87dd7c8, o=0xbfffee90) at kernel/qobject.cpp:2356
#13 0x41e4efce in QSignal::signal (this=0x84de2a8, t0=@0x84de2d0) at .moc/debug-shared-mt/moc_qsignal.cpp:100
#14 0x41b15c03 in QSignal::activate (this=0x84de2a8) at kernel/qsignal.cpp:212
#15 0x41b1d11f in QSingleShotTimer::event (this=0x84de280) at kernel/qtimer.cpp:277
#16 0x41a96113 in QApplication::internalNotify (this=0xbffff490, receiver=0x84de280, e=0xbffff120)
    at kernel/qapplication.cpp:2620
#17 0x41a955d0 in QApplication::notify (this=0xbffff490, receiver=0x84de280, e=0xbffff120) at kernel/qapplication.cpp:2343
#18 0x415d5ebf in KApplication::notify (this=0xbffff490, receiver=0x84de280, event=0xbffff120) at kapplication.cpp:495
#19 0x41a2c0d7 in QApplication::sendEvent (receiver=0x84de280, event=0xbffff120) at qapplication.h:491
#20 0x41a8422c in QEventLoop::activateTimers (this=0x80df530) at kernel/qeventloop_unix.cpp:558
#21 0x41a3e0dd in QEventLoop::processEvents (this=0x80df530, flags=4) at kernel/qeventloop_x11.cpp:389
#22 0x41aaa3b2 in QEventLoop::enterLoop (this=0x80df530) at kernel/qeventloop.cpp:198
#23 0x41aaa2ce in QEventLoop::exec (this=0x80df530) at kernel/qeventloop.cpp:145
#24 0x41a96297 in QApplication::exec (this=0xbffff490) at kernel/qapplication.cpp:2743
#25 0x0804a35c in main (argc=2, argv=0xbffff624) at kapplication.h:217
(gdb) q