Kernel bug prevents shutdown of Ubuntu 9.04

[meindian523]

My computer was booting,shutting down and rebooting normally enough upto the past few days before I had a kernel bug occur and prevent shutdown with a long list of hex numbers and services open at the time.Relevant part of the error:

[107.616395]------------[ cut here ]---------------------------
[107.616448]kernel BUG at /build/buildd/linux-2.6.28/arch/x86/mm/pat.c: 298!
[107.616494]invalid opcode: 0000 [#1] SMP

Similar issue here,only the latest open file changes from (attempted) shutdown to (attempted) shutdown,and my processor is Pentium D (2.80GHz).Same motherboard(D101GGC),no external graphics,internal graphics ATi Radeon XPRESS 200,512MB DDR1 RAM,and running 64 bit 9.04.What confuses me is that the path shows arch as x86 while I'm running x86_64

I'm presently shutting down using the emergency sequence Alt+SysRQ+RSEIUO
TIA for any and all help.

[meindian523]

bump

[lisati]

Are any of the bugs here relevant? One or two seem similar

[meindian523]

Didn't see any of them concerning pat.c,which is the file my bug points to.And I posted so I could ask for a workaround.

edit:Also,this bug occurred just a few days ago,the same kernel shutdown,restarted,etc nicely upto a few days ago.

[meindian523]

bump.workarounds?