Version:            (using KDE 4.2.2)
OS:                Linux
Installed from:    Ubuntu Packages

The situation:
There is one instance/window of kate with a textfile in the background, that is untouched.
I opened a second Instance of Kate by clicking on a quite small text file in dolphin. First time I added a line (paste, ctrl+v) saved the file ( 'Save' in the navigation toolbar) and then clicked 'Close' (also navigation toolbar). The result wasn't what I wanted. So I clicked 'File'->'quit'/'exit'? ('Beenden' in my German version.) inside the 'File'-menu. At this point this kate instance crashed and caused the signal 11 (SIGSEGV). The other instance in the background was not affected by the crash. 

The circumstances:
Kate v3.22 (from Kubuntu 9.04, alternate-amd64-DVD) was used in default configuration.
Other open applications: 1 Dolphin,  1 Kmail and 1 empty mail, 1 bash and 3 Konquerror instances/windows with 18 open tabs altogether. Important? System stability seems to be not affected by the bug.

The backtrace was empty. So I opened KPackageKit, installed kdelibs-dbg and some other -dbg-packages and closed KPackageKit.

After that I tried and reproduced the crash two times in the same constellation (all programms like mentioned above were still running) :
I opened a second Instance of Kate by clicking on (the same) text file in dolphin.
This time I didn't edit the file but immediately clicked 'Close' (navigation toolbar). Then I clicked 'File'->'quit'/'exit'? ('Beenden' in my German version.) inside the 'File'-menu. Again this kate instance crashed and caused the signal 11 (SIGSEGV).

Here is the backtrace (from the second reproduction):
Anwendung: Kate (kate), Signal SIGSEGV
0x00007f4038c43cf0 in __nanosleep_nocancel () from /lib/libc.so.6

Thread 1 (Thread 0x7f403c963750 (LWP 30881)):
[KCrash Handler]
#5  0x00007f403a7de3ce in QMenu::findIdForAction (this=0x2976c40, act=0x284f090) at widgets/qmenu.cpp:3157
#6  0x00007f403a7df8db in QMenuPrivate::activateCausedStack (this=0x298b160, causedStack=@0x7fff4498b790, action=0x284f090, action_e=QAction::Trigger, self=176) at widgets/qmenu.cpp:965
#7  0x00007f403a7e5a0e in QMenuPrivate::activateAction (this=0x298b160, action=0x284f090, action_e=QAction::Trigger, self=true) at widgets/qmenu.cpp:1058
#8  0x00007f403b8bcb71 in KMenu::mouseReleaseEvent (this=0x298dbd0, e=0x7fff4498c130) at /build/buildd/kde4libs-4.2.2/kdeui/widgets/kmenu.cpp:454
#9  0x00007f403a4078cf in QWidget::event (this=0x298dbd0, event=0x7fff4498c130) at kernel/qwidget.cpp:7516
#10 0x00007f403a7e81cb in QMenu::event (this=0x298dbd0, e=0x7fff4498c130) at widgets/qmenu.cpp:2351
#11 0x00007f403a3b678d in QApplicationPrivate::notify_helper (this=0x25e5c40, receiver=0x298dbd0, e=0x7fff4498c130) at kernel/qapplication.cpp:4084
#12 0x00007f403a3bf0da in QApplication::notify (this=<value optimized out>, receiver=0x298dbd0, e=0x7fff4498c130) at kernel/qapplication.cpp:3786
#13 0x00007f403b7eb26b in KApplication::notify (this=0x7fff4498d0c0, receiver=0x298dbd0, event=0x7fff4498c130) at /build/buildd/kde4libs-4.2.2/kdeui/kernel/kapplication.cpp:307
#14 0x00007f403980d75c in QCoreApplication::notifyInternal (this=0x7fff4498d0c0, receiver=0x298dbd0, event=0x7fff4498c130) at kernel/qcoreapplication.cpp:602
#15 0x00007f403a3be328 in QApplicationPrivate::sendMouseEvent (receiver=0x298dbd0, event=0x7fff4498c130, alienWidget=0x0, nativeWidget=0x298dbd0, buttonDown=<value optimized out>, 
    lastMouseReceiver=@0x7f403ae1aeb0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:216
#16 0x00007f403a427fd4 in QETWidget::translateMouseEvent (this=0x298dbd0, event=<value optimized out>) at kernel/qapplication_x11.cpp:4359
#17 0x00007f403a426a88 in QApplication::x11ProcessEvent (this=0x7fff4498d0c0, event=0x7fff4498cc70) at kernel/qapplication_x11.cpp:3543
#18 0x00007f403a44f464 in x11EventSourceDispatch (s=0x25e98c0, callback=0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:146
#19 0x00007f4034c5520a in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#20 0x00007f4034c588e0 in ?? () from /usr/lib/libglib-2.0.so.0
#21 0x00007f4034c58a7c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#22 0x00007f4039836e6f in QEventDispatcherGlib::processEvents (this=0x25d0b70, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:323
#23 0x00007f403a44ebef in QGuiEventDispatcherGlib::processEvents (this=0x2976c40, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#24 0x00007f403980c002 in QEventLoop::processEvents (this=<value optimized out>, flags={i = 1150865248}) at kernel/qeventloop.cpp:149
#25 0x00007f403980c3cd in QEventLoop::exec (this=0x7fff4498cfa0, flags={i = 1150865328}) at kernel/qeventloop.cpp:200
#26 0x00007f403980e694 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:880
#27 0x00007f403c56cc35 in kdemain () from /usr/lib/libkdeinit4_kate.so
#28 0x00007f4038bba5a6 in __libc_start_main (main=0x4007f0 <_start+240>, argc=2, ubp_av=0x7fff4498e2a8, init=0x400820 <__libc_csu_init>, fini=<value optimized out>, rtld_fini=<value optimized out>, 
    stack_end=0x7fff4498e298) at libc-start.c:220
#29 0x0000000000400729 in _start ()


My system:
AMD  Athlon X2 5050E, Gigabyte GA-M78G-DS3H, 4 GB RAM

So, this is my first Application crash bug report. I hope it's gonna be helpful!
James would have said:"I gid my vedy best!"
Tell me, please, what is missing, confusing or boring!