Version:           0.50.50 (using 4.00.62 (KDE 4.0.62 >= 20080213), Gentoo)
Compiler:          i686-pc-linux-gnu-gcc
OS:                Linux (i686) release 2.6.23-gentoo-r6

Kopete (kdenetwork r774901) had problems sending a message to an MSN contact, so I decided to close kopete (used ICQ, MSN and Jabber accounts). 
As I closed it, it crashed with the following backtrace (sems like some problem with the Jabber plugin?):

Application: Kopete (kopete), signal SIGABRT
Using host libthread_db library "/lib/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread 0xb5b5a6d0 (LWP 5812)]
[KCrash handler]
#6  0xffffe410 in __kernel_vsyscall ()
#7  0xb5f431f1 in *__GI_raise (sig=6)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#8  0xb5f449b8 in *__GI_abort () at abort.c:88
#9  0xb5f7fb78 in malloc_printerr (action=2, 
    str=0xb602bee4 "free(): invalid pointer", ptr=0x16b4) at malloc.c:5892
#10 0xb5f817e5 in *__GI___libc_free (mem=0x8483580) at malloc.c:3586
#11 0xb6130011 in operator delete ()
   from /usr/lib/gcc/i686-pc-linux-gnu/4.1.2/libstdc++.so.6
#12 0xb41e33bb in ~CoreProtocol (this=0x8483580)
    at /var/tmp/portage/kde-base/kdenetwork-9999.4/work/kdenetwork-9999.4/kopete/protocols/jabber/libiris/iris/xmpp-core/protocol.cpp:605
#13 0xb7e5edee in QObjectPrivate::deleteChildren (this=0x80c5b60)
    at kernel/qobject.cpp:1925
#14 0xb7e61c58 in ~QObject (this=0xbfc0dc68) at kernel/qobject.cpp:823
#15 0xb7e4e7bf in ~QCoreApplication (this=0xbfc0dc68)
    at kernel/qcoreapplication.cpp:478
#16 0xb6dc096a in ~QApplication (this=0xbfc0dc68)
    at kernel/qapplication.cpp:995
#17 0xb78f1e7d in ~KApplication (this=0xbfc0dc68)
    at /var/tmp/portage/kde-base/kdelibs-9999.4/work/kdelibs-9999.4/kdeui/kernel/kapplication.cpp:912
#18 0xb78f9e58 in ~KUniqueApplication (this=0xbfc0dc68)
    at /var/tmp/portage/kde-base/kdelibs-9999.4/work/kdelibs-9999.4/kdeui/kernel/kuniqueapplication.cpp:335
#19 0x0808a1de in ~KopeteApplication (this=0xbfc0dc68)
    at /var/tmp/portage/kde-base/kdenetwork-9999.4/work/kdenetwork-9999.4/kopete/kopete/kopeteapplication.cpp:108
#20 0x080893b6 in main (argc=)
    at /var/tmp/portage/kde-base/kdenetwork-9999.4/work/kdenetwork-9999.4/kopete/kopete/main.cpp:102
#21 0xb5f2ffdc in __libc_start_main (main=0x8087410 <main>, argc=3, 
    ubp_av=0xbfc0e054, init=0x8098920 <__libc_csu_init>, 
    fini=0x8098910 <__libc_csu_fini>, rtld_fini=0xb7f11100 <_dl_fini>, 
    stack_end=0xbfc0e04c) at libc-start.c:229
#22 0x08064481 in _start ()
#0  0xffffe410 in __kernel_vsyscall ()