IIS Worker Process encountered a poblem.

Hi All,
I keep getting this error on a Windows Server 2003 Sp1 DC,
“IIS Worker Process Encountered a problem and needed to close.”
It started happening after installing Sharepoint services, a few months ago. The sharepoint page drops out intermittently and the error appears. Acouple of times per day.
Can’t really find anything corresponding in the event logs.

I’ve run iisstate and generated logs for each iis process. I don’t know which process is the one that is failing but cannot receive any idea of what’s going wrong.

Has anyone been able to successfully diagnose this problem ? Do I need to run iisstate using sc or hc, on which process ?

Cheers