[CentOS] X Crashing on 64 Bit CentOS

Hi People,

I have a user who is regularly having X Crash.  This seemed to happen 
once a month but has increased to once or twice a week.  It doesn't seem 
to be application specific.  The only information about whats causing 
the crash is from the X log.  But this doesn't really give much to go on.

Backtrace:
0: /usr/bin/Xorg(xf86SigHandler+0x71) [0x4865b1]
1: /lib64/libc.so.6 [0x3475430280]
2: /usr/lib64/xorg/modules/libfb.so(fbCopyAreammx+0x274) [0x2b917c4dbe14]
3: /usr/lib64/xorg/modules/libfb.so(fbComposite+0x5db) [0x2b917c4cc65b]
4: /usr/lib64/xorg/modules/libxaa.so(XAAComposite+0x2ac) [0x2b917c71d94c]
5: /usr/bin/Xorg [0x51379d]
6: /usr/bin/Xorg [0x50fb54]
7: /usr/bin/Xorg [0x5032ef]
8: /usr/bin/Xorg(Dispatch+0x1ca) [0x449c9a]
9: /usr/bin/Xorg(main+0x44e) [0x4325ee]
10: /lib64/libc.so.6(__libc_start_main+0xf4) [0x347541d974]

Any suggestions as to how I diagnose this further?  I have just applied 
the latest update