Version:            (using KDE KDE 3.4.3)
Installed from:    Gentoo Packages
Compiler:          gcc 4.0.2 
OS:                Linux

Here's the backtrace:

It's possible this is a gcc 4.0.2 bug, as it seems to be happening on the destruction of a vector object, but I'll leave that for you to decide.

Using host libthread_db library "/lib/libthread_db.so.1".
`system-supplied DSO at 0xffffe000' has disappeared; keeping its symbols.
[Thread debugging using libthread_db enabled]
[New Thread -1248327232 (LWP 5064)]
[KCrash handler]
#4  0xb5bdb479 in __gnu_cxx::__pool<true>::_M_reclaim_block ()
   from /usr/lib/gcc/i686-pc-linux-gnu/4.0.2/libstdc++.so.6
#5  0xb7c92dc9 in __gnu_cxx::__mt_alloc<DwFieldBody*, __gnu_cxx::__common_pool_policy<__gnu_cxx::__pool, true> >::deallocate (this=0xbfecbadc, __p=0x84dc220, 
    __n=1) at mt_allocator.h:716
#6  0xb7c92e13 in std::_Vector_base<DwFieldBody*, std::allocator<DwFieldBody*> >::_M_deallocate (this=0xbfecbadc, __p=0x84dc220, __n=1) at stl_vector.h:123
#7  0xb7c92e4a in ~_Vector_base (this=0xbfecbadc) at stl_vector.h:109
#8  0xb7c92ea8 in ~vector (this=0xbfecbadc) at stl_vector.h:273
#9  0xb7c88b0d in KMMessage::headerFields (this=0x843da98, field=@0xbfecbb38)
    at kmmessage.cpp:2139
#10 0xb7c88b8f in KMMessage::cc (this=0x843da98) at kmmessage.cpp:1782
#11 0xb7e23db5 in KMail::FancyHeaderStyle::format (this=0x8295db0, 
    message=0x843da98, strategy=0x805f338, vCardName=@0xbfed140c, 
    printing=false) at headerstyle.cpp:624
#12 0xb7d4df77 in KMReaderWin::writeMsgHeader (this=0x82a4b98, aMsg=0x843da98, 
    hasVCard=false) at kmreaderwin.cpp:1538
#13 0xb7d4f6fd in KMReaderWin::parseMsg (this=0x82a4b98, aMsg=0x843da98)
    at kmreaderwin.cpp:1421
#14 0xb7d503af in KMReaderWin::displayMessage (this=0x82a4b98)
    at kmreaderwin.cpp:1360
#15 0xb7d5054e in KMReaderWin::updateReaderWin (this=0x82a4b98)
    at kmreaderwin.cpp:1302
#16 0xb7d50875 in KMReaderWin::update (this=0x82a4b98, observable=0x843dab4)
    at kmreaderwin.cpp:808
#17 0xb7e95def in KMail::ISubject::notify (this=0x843dab4) at isubject.cpp:35
#18 0xb7c861b1 in KMMessage::updateBodyPart (this=0x843da98, 
    partSpecifier=@0xbfed1a94, data=@0x8468aa8) at kmmessage.cpp:4016
#19 0xb7e832a9 in KMail::ImapJob::slotGetMessageResult (this=0x8467758, 
    job=0x8468900) at imapjob.cpp:403
#20 0xb7e856f7 in KMail::ImapJob::qt_invoke (this=0x8467758, _id=2, 
    _o=0xbfed1b54) at imapjob.moc:126
#21 0xb61fd916 in QObject::activate_signal () from /usr/qt/3/lib/libqt-mt.so.3
#22 0xb6d98988 in KIO::Job::result () from /usr/kde/3.4/lib/libkio.so.4
#23 0xb6da1110 in KIO::Job::emitResult () from /usr/kde/3.4/lib/libkio.so.4
#24 0xb6da6260 in KIO::SimpleJob::slotFinished ()
   from /usr/kde/3.4/lib/libkio.so.4
#25 0xb6da7c13 in KIO::TransferJob::slotFinished ()
   from /usr/kde/3.4/lib/libkio.so.4
#26 0xb6d9cbdb in KIO::TransferJob::qt_invoke ()
   from /usr/kde/3.4/lib/libkio.so.4
#27 0xb61fd916 in QObject::activate_signal () from /usr/qt/3/lib/libqt-mt.so.3
#28 0xb61fdd14 in QObject::activate_signal () from /usr/qt/3/lib/libqt-mt.so.3
#29 0xb6d898a0 in KIO::SlaveInterface::finished ()
   from /usr/kde/3.4/lib/libkio.so.4
#30 0xb6d8c364 in KIO::SlaveInterface::dispatch ()
   from /usr/kde/3.4/lib/libkio.so.4
#31 0xb6d8a7cb in KIO::SlaveInterface::dispatch ()
   from /usr/kde/3.4/lib/libkio.so.4
#32 0xb6d87cf0 in KIO::Slave::gotInput () from /usr/kde/3.4/lib/libkio.so.4
#33 0xb6d87e85 in KIO::Slave::qt_invoke () from /usr/kde/3.4/lib/libkio.so.4
#34 0xb61fd916 in QObject::activate_signal () from /usr/qt/3/lib/libqt-mt.so.3
#35 0xb61fde3a in QObject::activate_signal () from /usr/qt/3/lib/libqt-mt.so.3
#36 0xb6543838 in QSocketNotifier::activated ()
   from /usr/qt/3/lib/libqt-mt.so.3
#37 0xb621afdd in QSocketNotifier::event () from /usr/qt/3/lib/libqt-mt.so.3
#38 0xb619dc1d in QApplication::internalNotify ()
   from /usr/qt/3/lib/libqt-mt.so.3
#39 0xb619e3a0 in QApplication::notify () from /usr/qt/3/lib/libqt-mt.so.3
#40 0xb67e9a13 in KApplication::notify () from /usr/kde/3.4/lib/libkdecore.so.4
#41 0xb6192209 in QEventLoop::activateSocketNotifiers ()
   from /usr/qt/3/lib/libqt-mt.so.3
#42 0xb61476f6 in QEventLoop::processEvents () from /usr/qt/3/lib/libqt-mt.so.3
#43 0xb61b4032 in QEventLoop::enterLoop () from /usr/qt/3/lib/libqt-mt.so.3
#44 0xb61b3f56 in QEventLoop::exec () from /usr/qt/3/lib/libqt-mt.so.3
#45 0xb619d471 in QApplication::exec () from /usr/qt/3/lib/libqt-mt.so.3
#46 0x0804aa00 in main (argc=7, argv=0xbfed29a4) at main.cpp:95