If you're concerned about any other logs being cleared, e.g the system or application logs, or even a windows event log made by a 3rd party application, Windows 2008 produces Event ID 104 in the System log whever that happens. This shows "Whodunit" in the "User" field (unlike all security events in 2008, where they abandoned the User field...! ), and the Description will tell you the log name.
Hope this helps...!