I was diagnosing performance problems for a customer when several performance-related counters suddenly stopped working. The affected information included all SQL Server Performance Monitor counters, waittype information from sysprocesses, and all I/O-related activity from the fn_virtualfilestats() function. I was confused until I ran across the Microsoft article "FIX: 'Performance monitor shared memory setup failed: -1' error message when you start SQL Server" at http://support.microsoft.com/de...