Kernel bug at boot

This is kernel 2.6.11.7, with debian patches applied.
Motherboard: Tyan Tiger
Processors: 2 x Opteron
2Gb memory

I get this message at boot time.  This did not happen earlier, so I
suspect it is to do with temperature, which has risen considerably
during the day.

Turning the machine off for 10 minutes also made it go away.

...
Freeing unused kernel memory: 236k freed
BUG: using smp_processor_id() in preemptible [00000001] code: swapper/0
caller is k7_machine_check+0x38/0x1c0
 [<c01d7566>] smp_processor_id+0xa6/0xc0
 [<c010b578>] k7_machine_check+0x38/0x1c0
 [<c010b578>] k7_machine_check+0x38/0x1c0
 [<c01225a2>] __do_softirq+0x62/0xd0
 [<c010b540>] k7_machine_check+0x0/0x1c0
 [<c0103d5f>] error_code+0x2b/0x30
 [<c0101053>] default_idle+0x23/0x30
 [<c01010f3>] cpu_idle+0x53/0x60
CPU 1: Machine Check Exception: 0000000000000007
Bank 4: f401a00000000a13 at 000000007ff80028
Kernel panic - not syncing: unable to continue
-- 
Oliver Elphick <[email protected]>
Bray Health and Leisure