Application: knotify4 (4.0)
KDE Platform Version: 4.10.00
Qt Version: 4.8.2
Operating System: Linux 3.5.0-18-generic x86_64
Distribution: Ubuntu 12.04.2 LTS

-- Information about the crash:
knotify was not working so I used the console to restart it, the output was:

cabalbl4@kos-mos:~$ knotify4 --waitforwm
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbeh
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbeh
X Error: BadAtom (invalid Atom parameter) 5
  Major opcode: 20 (X_GetProperty)
  Resource id:  0x0
KCrash: Application 'knotify4' crashing...
KCrash: Attempting to start /usr/lib/kde4/libexec/drkonqi from kdeinit
sock_file=/home/cabalbl4/.kde/socket-kos-mos/kdeinit4__0
unnamed app(24139): Communication problem with  "knotify" , it probably crashed. 
Error message was:  "org.freedesktop.DBus.Error.NoReply" : " "Message did not receive a reply (ti by message bus)" " 

It started properly later.

The crash can be reproduced some of the time.

-- Backtrace:
Application: KNotify (knotify4), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[KCrash Handler]
#6  __GI___libc_free (mem=0x1) at malloc.c:2968
#7  0x00007fc551976819 in XFree () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#8  0x00007fc5549e74c2 in KApplicationPrivate::parseCommandLine (this=0x99bb00) at ../../kdeui/kernel/kapplication.cpp:875
#9  0x00007fc5549e9f1c in KApplicationPrivate::init (this=0x99bb00, GUIenabled=true) at ../../kdeui/kernel/kapplication.cpp:478
#10 0x00007fc5549eaabb in KApplication::KApplication (this=0x7fff8b2f2990, GUIenabled=true, cData=...) at ../../kdeui/kernel/kapplication.cpp:387
#11 0x00007fc5549efe15 in KUniqueApplication::KUniqueApplication (this=0x7fff8b2f2990, GUIenabled=true, configUnique=<optimized out>) at ../../kdeui/kernel/kuniqueapplication.cpp:314
#12 0x000000000040996d in main (argc=2, argv=0x7fff8b2f2d18) at ../../knotify/main.cpp:61

Reported using DrKonqi