Event Log Rules

We had created a new Event Log rule (for the Application Log) with just Event Type = Error checked off, and Alert with Severity = Critical. This was almost the same as the predefined "Any Application Failure" which has Event Type = Error and Warning checked off. The new event log rule seemed to be working, but now it is not, and we cannot figure out why. We're getting plenty of Application log events logged with type Error, and users that have the "Any Application Failure" rule in their notification profile get the alarm, but those with the custom rule do not, even though the Event type is only Error.

Any suggestions?

We're using build 5510. Both the OpMan server and the server whose log we're monitoring are Windows 2000 machines.