A trace using gdb on karmic.  Application (patched version of apport-kde) crashes on exit.  The run and exit code:

    # Don't exec_() here.  There is no main interface and the dialogs are
    #  exec_()ed independently.
    ret = int(UserInterface.run_argv())
    print "run_argv returned"
    KApplication.exit(ret)
    print "kapplication.exit returned"
    sys.exit(ret)

The output and trace:
run_argv returned
kapplication.exit returned

Program received signal SIGSEGV, Segmentation fault.
0x052c1ce2 in ~QX11WindowSurface (this=0x8ad3e20, __in_chrg=<value optimized out>) at painting/qwindowsurface_x11.cpp:84
84      painting/qwindowsurface_x11.cpp: No such file or directory.
        in painting/qwindowsurface_x11.cpp
Current language:  auto; currently c++
(gdb) backtrace
#0  0x052c1ce2 in ~QX11WindowSurface (this=0x8ad3e20, __in_chrg=<value optimized out>) at painting/qwindowsurface_x11.cpp:84
#1  0x052ba946 in ~QWidgetBackingStore (this=0x8ad3df0, __in_chrg=<value optimized out>) at painting/qbackingstore.cpp:829
#2  0x0511c944 in QWidgetPrivate::deleteExtra (this=0x8aadf30) at kernel/qwidget.cpp:1503
#3  0x0511d0e5 in ~QWidgetPrivate (this=0x8aadf30, __in_chrg=<value optimized out>) at kernel/qwidget.cpp:227
#4  0x055a6189 in ~QDialogPrivate (this=0x8aadf30, __in_chrg=<value optimized out>) at ../../include/QtGui/private/../../../src/gui/dialogs/qdialog_p.h:67
#5  0x005de85a in ~QObject (this=0x8b825d8, __in_chrg=<value optimized out>) at kernel/qobject.cpp:857
#6  0x0512294f in ~QWidget (this=0x8b825d8, __in_chrg=<value optimized out>) at kernel/qwidget.cpp:1380
#7  0x055bde44 in ~QDialog (this=0x8b825d8, __in_chrg=<value optimized out>) at dialogs/qdialog.cpp:298
#8  0x01278653 in ?? () from /usr/lib/pymodules/python2.6/PyQt4/QtGui.so
#9  0x012177a6 in ?? () from /usr/lib/pymodules/python2.6/PyQt4/QtGui.so
#10 0x012177e9 in ?? () from /usr/lib/pymodules/python2.6/PyQt4/QtGui.so
#11 0x0038d588 in ?? () from /usr/lib/pymodules/python2.6/sip.so
#12 0x0038d5c1 in ?? () from /usr/lib/pymodules/python2.6/sip.so
#13 0x080a8e13 in subtype_dealloc (self=0x8baf4ac) at ../Objects/typeobject.c:1024
#14 0x0808e574 in dict_dealloc (mp=0x88464f4) at ../Objects/dictobject.c:911
#15 0x0806a3eb in instance_dealloc (inst=0x8cc1a8c) at ../Objects/classobject.c:668
#16 0x0808ce59 in insertdict (mp=0xb7fd61c4, key=0xb7ebb4a8, hash=-414803461, value=0x8245f58) at ../Objects/dictobject.c:459
#17 0x0808f2b7 in PyDict_SetItem (op=0xb7fd61c4, key=0xb7ebb4a8, value=0x8245f58) at ../Objects/dictobject.c:701
#18 0x08090c13 in _PyModule_Clear (m=0xb7fa411c) at ../Objects/moduleobject.c:138
#19 0x080ed7a5 in PyImport_Cleanup () at ../Python/import.c:444
#20 0x080fa0d5 in Py_Finalize () at ../Python/pythonrun.c:434
#21 0x080f9b7f in Py_Exit () at ../Python/pythonrun.c:1714
#22 handle_system_exit () at ../Python/pythonrun.c:1116
#23 0x080f9d6d in PyErr_PrintEx (set_sys_last_vars=1) at ../Python/pythonrun.c:1126
#24 0x080f9fa2 in PyErr_Print () at ../Python/pythonrun.c:1035
#25 0x080faacb in PyRun_SimpleFileExFlags (fp=0xbffffa8b, filename=0xbffffa8b "/usr/share/apport/apport-kde", closeit=1, flags=0xbffff80c) at ../Python/pythonrun.c:935
#26 0x0805c898 in Py_Main (argc=3, argv=0xbffff8f4) at ../Modules/main.c:599
#27 0x0805baab in main (argc=3, argv=0xbffff8f4) at ../Modules/python.c:23

The behavior is the same with or without the KApplication.exit()