Why has my system rebooted?

2007-12-25 1:55:00

Hi Managers,
What does :-
Aug 29 22:06:15 brscs02 unix: NOTICE: Scheduling clearing of error on page
0x000
00001.e0a84000
Aug 29 22:06:15 brscs02 unix: WARNING: [AFT1] initiating reboot due to above
err

INIT: New run level: 6
The system is coming down. Please wait.
System services are now being stopped.