Version:           unknown (using KDE 3.5.8, Kubuntu (gutsy) 4:3.5.8-0ubuntu3.1)
Compiler:          Target: i486-linux-gnu
OS:                Linux (i686) release 2.6.22-14-generic

After some experiments with toolbar - mainly, I've just added 2 sets of buttons "Spam", "Not Spam" to 2 different toolbars (don't remember correctly, but i think to kmail and to kontact toolbars) - and now Kontact crashes on startup.

Backtrace:

Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1243633168 (LWP 8031)]
[New Thread -1288479856 (LWP 8039)]
[New Thread -1280087152 (LWP 8038)]
[New Thread -1271694448 (LWP 8037)]
[New Thread -1263301744 (LWP 8036)]
[KCrash handler]
#6  0xb517023b in typeinfo for KMFilterCommand ()
   from /usr/lib/libkmailprivate.so
#7  0xec080774 in ?? ()
#8  0xb700d6d0 in KXMLGUI::ActionList::unplug (this=0x85f2fac, 
    container=0x81fd468)
    at /build/buildd/kdelibs-3.5.8/./kdeui/kxmlguifactory_p.cpp:44
#9  0xb70af5c5 in KXMLGUI::ContainerNode::unplugClient (this=0x8208a70, 
    client=0x85f2fa8)
    at /build/buildd/kdelibs-3.5.8/./kdeui/kxmlguifactory_p.cpp:426
#10 0xb70af84c in KXMLGUI::ContainerNode::unplugActions (this=0x8208a70, 
    state=@0x81f3af8)
    at /build/buildd/kdelibs-3.5.8/./kdeui/kxmlguifactory_p.cpp:406
#11 0xb70af8af in KXMLGUI::ContainerNode::destruct (this=0x8208a70, 
    element=@0xbfe2d3e4, state=@0x81f3af8)
    at /build/buildd/kdelibs-3.5.8/./kdeui/kxmlguifactory_p.cpp:313
#12 0xb70afaaa in KXMLGUI::ContainerNode::destructChildren (this=0x81f3c58, 
    element=@0xbfe2d520, state=@0x81f3af8)
    at /build/buildd/kdelibs-3.5.8/./kdeui/kxmlguifactory_p.cpp:358
#13 0xb70af89d in KXMLGUI::ContainerNode::destruct (this=0x81f3c58, 
    element=@0xbfe2d520, state=@0x81f3af8)
    at /build/buildd/kdelibs-3.5.8/./kdeui/kxmlguifactory_p.cpp:311
#14 0xb70bb7e1 in KXMLGUIFactory::removeClient (this=0x81ee510, 
    client=0x83fafe0)
    at /build/buildd/kdelibs-3.5.8/./kdeui/kxmlguifactory.cpp:364
#15 0xb758e57a in KParts::MainWindow::createGUI (this=0x80e08b0, 
    part=0x83faf58) at /build/buildd/kdelibs-3.5.8/./kparts/mainwindow.cpp:108
#16 0x08062aed in ?? ()
#17 0x080e08b0 in ?? ()
#18 0x083faf58 in ?? ()
#19 0xbfe2d640 in ?? ()
#20 0x08215148 in ?? ()
#21 0xb5f7314c in ?? () from /lib/tls/i686/cmov/libc.so.6
#22 0x083faf58 in ?? ()
#23 0x080e09c0 in ?? ()
#24 0xb6091ff4 in ?? () from /usr/lib/libstdc++.so.6
#25 0x00000014 in ?? ()
#26 0x08224928 in ?? ()
#27 0x08224ba8 in ?? ()
#28 0xb605f6a7 in operator new () from /usr/lib/libstdc++.so.6
#29 0x08061073 in ?? ()
#30 0x080e08b0 in ?? ()
#31 0x08241640 in ?? ()
#32 0x080e08b0 in ?? ()
#33 0x081e8f08 in ?? ()
#34 0x080770d8 in typeinfo for Kontact::Core ()
#35 0x0000000a in ?? ()
#36 0xb73bce80 in KFileMetaInfo (this=0x80e08b0, path=@0xbfe2d714, 
    mimeType=@0x0, what=0)
    at /build/buildd/kdelibs-3.5.8/./kio/kio/kfilemetainfo.cpp:304
#37 0x08061216 in ?? ()
#38 0x080e08b0 in ?? ()
#39 0xbfe2d714 in ?? ()
#40 0x00000000 in ?? ()

Konsole output:
~$ kontact
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
kdecore (KAction): WARNING: KAction::plugAccel(): call to deprecated action.
*** KMail got signal 11 (Crashing)
ERROR: Communication problem with kontact, it probably crashed.