Version:            (using Devel)
Compiler:          gcc (SUSE Linux) 4.3.1 20080507 (prerelease) 
OS:                Linux
Installed from:    Compiled sources

I used kmail/kde4 for the first time and wanted to create a new mail.
The first mail worked, on the second mail I got this crash dump:

Application: KMail (kmail), signal SIGABRT
 [?1034h[Thread debugging using libthread_db enabled]
[Current thread is 0 (LWP 20850)]

Thread 2 (Thread 0xb2712b90 (LWP 20853)):
#0  0xffffe430 in __kernel_vsyscall ()
#1  0xb4969ef1 in select () from /lib/libc.so.6
#2  0xb56afe67 in ?? () from /usr/lib/libQtCore.so.4
#3  0xb55e084e in ?? () from /usr/lib/libQtCore.so.4
#4  0xb6014175 in start_thread () from /lib/libpthread.so.0
#5  0xb4970dce in clone () from /lib/libc.so.6

Thread 1 (Thread 0xb3d0d9b0 (LWP 20850)):
[KCrash Handler]
#6  0xffffe430 in __kernel_vsyscall ()
#7  0xb48cd900 in raise () from /lib/libc.so.6
#8  0xb48cf238 in abort () from /lib/libc.so.6
#9  0xb55d88c5 in qt_message_output () from /usr/lib/libQtCore.so.4
#10 0xb55d89a2 in qFatal () from /usr/lib/libQtCore.so.4
#11 0xb55d8a35 in qt_assert () from /usr/lib/libQtCore.so.4
#12 0xb7ebc8d8 in KCompletionBox::calculateGeometry (this=0x86ecb50) at /home/KDE4/source/kdelibs/kdeui/widgets/kcompletionbox.cpp:354
#13 0xb7ebca2c in KCompletionBox::sizeHint (this=0x86ecb50) at /home/KDE4/source/kdelibs/kdeui/widgets/kcompletionbox.cpp:402
#14 0xb7ebd543 in KCompletionBox::setItems (this=0x86ecb50, items=@0xbfad2108) at /home/KDE4/source/kdelibs/kdeui/widgets/kcompletionbox.cpp:551
#15 0xb7189693 in KPIM::AddresseeLineEdit::setCompletedItems (this=0x8452cc0, items=@0xbfad2108, autoSuggest=false) at /home/KDE4/source/kdepim/libkdepim/addresseelineedit.cpp:794
#16 0xb718c514 in KPIM::AddresseeLineEdit::doCompletion (this=0x8452cc0, ctrlT=false) at /home/KDE4/source/kdepim/libkdepim/addresseelineedit.cpp:420
#17 0xb718d255 in KPIM::AddresseeLineEdit::slotCompletion (this=0x8452cc0) at /home/KDE4/source/kdepim/libkdepim/addresseelineedit.cpp:927
#18 0xb718d36b in KPIM::AddresseeLineEdit::qt_metacall (this=0x8452cc0, _c=QMetaObject::InvokeMetaMethod, _id=5, _a=0xbfad229c) at /home/KDE4/build/kdepim/libkdepim/addresseelineedit.moc:90
#19 0xb763560a in KMLineEdit::qt_metacall (this=0x8452cc0, _c=QMetaObject::InvokeMetaMethod, _id=78, _a=0xbfad229c) at /home/KDE4/build/kdepim/kmail/kmlineeditspell.moc:67
#20 0xb76b216a in RecipientLineEdit::qt_metacall (this=0x8452cc0, _c=QMetaObject::InvokeMetaMethod, _id=78, _a=0xbfad229c) at /home/KDE4/build/kdepim/kmail/recipientseditor.moc:120
#21 0xb56e5730 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#22 0xb56e64b2 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#23 0xb7eda5c3 in KLineEdit::completion (this=0x8452cc0, _t1=@0xbfad238c) at /media/disk/KDE4/build/kdelibs/kdeui/klineedit.moc:219
#24 0xb7eda772 in KLineEditPrivate::doCompletion (this=0x85d5510, txt=@0xbfad238c) at /home/KDE4/source/kdelibs/kdeui/widgets/klineedit.cpp:1699
#25 0xb7ede7c9 in KLineEdit::keyPressEvent (this=0x8452cc0, e=0xbfad29ec) at /home/KDE4/source/kdelibs/kdeui/widgets/klineedit.cpp:906
#26 0xb718d4d4 in KPIM::AddresseeLineEdit::keyPressEvent (this=0x8452cc0, e=0xbfad29ec) at /home/KDE4/source/kdepim/libkdepim/addresseelineedit.cpp:205
#27 0xb763536e in KMLineEdit::keyPressEvent (this=0x8452cc0, e=0xbfad29ec) at /home/KDE4/source/kdepim/kmail/kmlineeditspell.cpp:74
#28 0xb76b3f48 in RecipientLineEdit::keyPressEvent (this=0x8452cc0, ev=0xbfad29ec) at /home/KDE4/source/kdepim/kmail/recipientseditor.cpp:141
#29 0xb4d2990e in QWidget::event () from /usr/lib/libQtGui.so.4
#30 0xb5074f97 in QLineEdit::event () from /usr/lib/libQtGui.so.4
#31 0xb7ee07ea in KLineEdit::event (this=0x8452cc0, ev=0xbfad29ec) at /home/KDE4/source/kdelibs/kdeui/widgets/klineedit.cpp:1295
#32 0xb4cd182c in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#33 0xb4cda7a6 in QApplication::notify () from /usr/lib/libQtGui.so.4
#34 0xb7dfd9ad in KApplication::notify (this=0xbfad34b8, receiver=0x8452cc0, event=0xbfad29ec) at /home/KDE4/source/kdelibs/kdeui/kernel/kapplication.cpp:307
#35 0xb56d0a61 in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#36 0xb4d324ee in ?? () from /usr/lib/libQtGui.so.4
#37 0xb4d675a0 in ?? () from /usr/lib/libQtGui.so.4
#38 0xb4d69716 in ?? () from /usr/lib/libQtGui.so.4
#39 0xb4d41bed in QApplication::x11ProcessEvent () from /usr/lib/libQtGui.so.4
#40 0xb4d6b1bc in ?? () from /usr/lib/libQtGui.so.4
#41 0xb44612d9 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#42 0xb446485b in ?? () from /usr/lib/libglib-2.0.so.0
#43 0xb44649d8 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#44 0xb56fb1f8 in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#45 0xb4d6a885 in ?? () from /usr/lib/libQtGui.so.4
#46 0xb56cf13a in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#47 0xb56cf2fa in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#48 0xb56d1995 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#49 0xb4cd16a7 in QApplication::exec () from /usr/lib/libQtGui.so.4
#50 0x0804a9a0 in main (argc=) at /home/KDE4/source/kdepim/kmail/main.cpp:146