Troubleshooting System Process - Need Help Please

Hi guys,

i got a windows 2003 sp2 server that runs microsoft's SCOM monitoring
tool and SQL.

every once in a while it experiences frequent maxing out of CPU by the
System process.

I tried disabling antivirus & some other services, it didn't help...
rebooting seems to help for a few days, and then it's back.

If i open the System process Threads using latest version of Proc
Explorer, I always see the thread that maxes out the cpu is
"ntoskrnl.exe!MiModifiedPageWriter"... if I click on the Stack button
it gives this error:

"Cannot access stack information. The stack may be swapped out,
Process Explorer cannot access the support in the Windows Debugging
Tools, or you previously ran an old version of Process Explorer and
must reboot"

I have the symbols configured and If i click Stack on some other
system process (like one of the svchost.exe's) it works. I did use an
older version before but rebooted. I also tried to run the tool as
SYSTEM and it didn't help.

any idea how to further troubleshoot or solve the Proc Explorer
issue? i'm assuming seeing the Stack will be necessary to solve it.

Thanks so much for any advice!!

ben
.