We recently performed an in-place SQL upgrade on a Windows Server 2008 R2 failover cluster, going from SQL 2005 SP4 to SQL 2008 R2 SP1. The upgrade process went smoothly, although afterwards we could no longer do performance monitoring for the SQL Network Name. When attempting this, it simply reports "Unable to connect to machine". Even more odd, we are able to use the IP address of the SQL Server with Performance Monitor. I am certain there is no DNS or network connectivity issue. The same problem exists when logged on locally to the active node. Has anyone seen this before? How do I troubleshoot this issue?
Thanks!