Application that crashed: kontact
Version of the application: 4.3.0
KDE Version: 4.3.00 (KDE 4.3.0)
Qt Version: 4.5.2
Operating System: Linux 2.6.31-desktop-0.rc5.3.1mnb x86_64
Distribution: "Mandriva Linux 2010.0"

What I was doing when the application crashed:
i close kontact and crash.
try kontact I fisrt time .
Have juste configure 2 IMAP account in kmail for 1 identitie
I hope that help you 

 -- Backtrace:
Application: Kontact (kontact), signal: Segmentation fault
[KCrash Handler]
#5  0x00007f54e16cc7a0 in QListData::shared_null () from /usr/lib64/libQtCore.so.4
#6  0x00007f54decac126 in qDeleteAll<QList<KIO::Slave*>::const_iterator> (begin=) at /usr/lib/qt4/include/QtCore/qalgorithms.h:350
#7  0x00007f54decac9dc in qDeleteAll<QList<KIO::Slave*> > (c=@0x7fff8d79f950) at /usr/lib/qt4/include/QtCore/qalgorithms.h:358
#8  0x00007f54decad15c in ~ProtocolInfo (this=0x2a6cd10) at /usr/src/debug/kdelibs-4.3.0/kio/kio/scheduler.cpp:171
#9  0x00007f54decad1d8 in qDeleteAll<QHash<QString, KIO::SchedulerPrivate::ProtocolInfo*>::const_iterator> (begin={i = 0x18a3640}, end={i = 0x11779e0})
    at /usr/lib/qt4/include/QtCore/qalgorithms.h:350
#10 0x00007f54decad41a in ~SchedulerPrivate (this=0x11102b0) at /usr/src/debug/kdelibs-4.3.0/kio/kio/scheduler.cpp:103
#11 0x00007f54deca7e12 in destroy () at /usr/src/debug/kdelibs-4.3.0/kio/kio/scheduler.cpp:209
#12 0x00007f54e00c5242 in ?? () from /lib64/libc.so.6
#13 0x00007f54e00c5295 in exit () from /lib64/libc.so.6
#14 0x00007f54e00af924 in __libc_start_main () from /lib64/libc.so.6
#15 0x0000000000402b59 in _start ()

Reported using DrKonqi