This error message returned by the SQL Server Advanced Monitor indicates that Uptime Infrastructure Monitor is not able to find the SQL Server performance counters on the target server.  Check the following items if this occurs:

• Is the hostname / instance name correct?  Try the monitor with and without an instance name to verify if that changes the scenario.
• Is the DB running SQL 2005 or 2008 with named instances?  If so, there are known issues when monitoring these environments if a specific counter fix has not been applied to the system.
• Restart the up.time Agent as it may have started when SQL Server was not yet online.
• Manually verify that the SQL 2000 performance counter objects exist.