The server in question was once a SQL2000 cluster and had been upgraded by some means to SQL2005, following this when opening Cluster Administrator the following error is displayed immediately.

An error occurred attempting to read properties for the 'Microsoft Search Service Instance' resource type: The specified node does not support a resource of this type. This may be due to version inconsistencies or due to the absence of the resource DLL on this node.

The error reported looks very much like the problem reported in article:

http://support.microsoft.com/kb/298147

You receive an "Invalid Class String" error when SQL Server connects to a Cluster Server through the Cluster Administrator

Which suggests that a DLL called 'Gathercl.dll' is missing.

Running FileMon does indeed show that the process ResrcMon.exe is looking for the above file and cannot find it -> from filemon:

119         02:41:13 PM       ResrcMon.exe:3892        QUERY INFORMATION  C:\WINDOWS\Cluster\gathercl.dll           NOT FOUND                Attributes: Error

But Gathercl.dll does not exist on other SQL2005 clusters either and they don’t have problems.

Now here is where we need to take a sanity check, there was a change between SQL2000 and SQL2005 with regard to the resource type for Full Text Search, in SQL2000 there was a custom resource DLL called …. GATHERCL.DLL, but in SQl2005 this changed and the Full Text search since this cluster was originally SQL2000 and has been upgraded we can assume that there is something that has not been tidied up as it should.

The resource types are listed in the following registry key

                HKLM\Cluster\ResourceTypes

The scrap  be removed using standard cluster.exe commands:

http://technet.microsoft.com/en-us/library/cc723245.aspx

CLUSTER [cluster name] RESOURCETYPE [resource type display name] /Delete /Type

Once this is done there should be no problem in opening Cluster Administrator.