I have seen this message in my event logs before, but being that it relates to
PerfMon I never bothered to see what caused it. Anyway, I looked it up and it has to do (at least for Windows 2003) with applying Windows Service Pack 2. This information can be found in the Microsoft article located here: http://support.microsoft.com/kb/932813/
The solution is, to run the following command:
Incidentally if you are getting a lot of messages related to Perflib, you can choose to rebuild all of the performance counters using the command:
This will update the system with the proper information and cause these EventLog messages to cease.