Here is handy commands to find crash information on Cisco 12000 router.
The below commands will show the following information: Crashing, Stack trace, Software version and reason of system reset
Cisco_Router#sh context sum
Cisco_Router#sh context sum
CRASH INFO SUMMARY
Slot 0 : 0 crashes
Slot 1 : 0 crashes
Slot 2 : 0 crashes
Slot 3 : 0 crashes
Slot 4 : 0 crashes
Slot 5 : 1 crashes
1 – crash at 07:03:09 UTC Sun May 31 2009
Slot 6 : 0 crashes
Slot 7 : 0 crashes
RESET INFO SUMMARY
Slot 0 : 0 resets
Slot 1 : 0 resets
Slot 2 : 0 resets
Slot 3 : 0 resets
Slot 4 : 0 resets
Slot 5 : 0 resets
Slot 6 : 0 resets
Slot 7 : 0 resets
Cisco_Router#
If you want to more details, type "Cisco_Router#sh context slot 5"