Recently, I had looked into a SQL Server 2008 cluster setup failure where the following information was noted in the Detail.txt file:

2011-02-21 11:58:37 Slp: Configuration action failed for feature SQL_Engine_Core_Inst during timing ConfigRC and scenario ConfigRC.
2011-02-21 11:58:37 Slp: The RPC server is unavailable
2011-02-21 11:58:37 Slp: Configuration action failed for feature SQL_Engine_Core_Inst during timing ConfigRC and scenario ConfigRC.
2011-02-21 11:58:37 Slp: System.ComponentModel.Win32Exception: The RPC server is unavailable
2011-02-21 11:58:37 Slp:    at Microsoft.SqlServer.Configuration.Cluster.ClusterResource.UpgradeResourceDLL(String nodeName, String dllPathName)
2011-02-21 11:58:37 Slp:    at Microsoft.SqlServer.Configuration.SqlEngine.SQLEngineClusterFeature.UpgradeResourceDLL(SQLServiceResource sqlResource)
2011-02-21 11:58:37 Slp:    at Microsoft.SqlServer.Configuration.SqlEngine.SQLEngineClusterFeature.ConfigureSQLEngineResourceType()
2011-02-21 11:58:37 Slp:    at Microsoft.SqlServer.Configuration.SqlEngine.SqlEngineSetupPrivate.Patch_ConfigRC(EffectiveProperties properties)
2011-02-21 11:58:37 Slp:    at Microsoft.SqlServer.Configuration.SqlEngine.SqlEngineSetupPrivate.Patch(ConfigActionTiming timing, Dictionary`2 actionData, PublicConfigurationBase spcb)
2011-02-21 11:58:37 Slp:    at Microsoft.SqlServer.Configuration.SqlConfigBase.SqlFeatureConfigBase.Execute(ConfigActionScenario scenario, ConfigActionTiming timing, Dictionary`2 actionData, PublicConfigurationBase spcbCurrent)
2011-02-21 11:58:37 Slp:    at Microsoft.SqlServer.Configuration.SqlConfigBase.SlpConfigAction.ExecuteAction(String actionId)
2011-02-21 11:58:37 Slp:    at Microsoft.SqlServer.Configuration.SqlConfigBase.SlpConfigAction.Execute(String actionId, TextWriter errorStream)
2011-02-21 11:58:37 Slp: Exception: System.ComponentModel.Win32Exception.
2011-02-21 11:58:37 Slp: Source: Microsoft.SqlServer.Configuration.Cluster.
2011-02-21 11:58:37 Slp: Message: The RPC server is unavailable.

The RPC Server is unavailable is a pretty generic error and can happen due to a lot of reasons. One of the common reasons that we have seen in CSS while troubleshooting setup issues is with incorrect DNS entries. This can happen if DNS entry for the cluster network name wasn’t configured properly and is pointing to an incorrect IP Address.

Another point to keep in mind is Windows Firewall. Make sure that the Firewall configuration allows this RPC call through.

I worked with Shahryar (Twitter) on a similar issue last week and it was identified that a PING request to the cluster name or IP returned no response.

If all else fails, then network tracing would help in figuring out what is failing and where.

References:

Error message when you connect to a cluster virtual server by using the named pipes protocol: "The machines selected for remote communication is not available at this time."
http://support.microsoft.com/kb/306985/