Just when I thought I had cleared out all my WMI woes, they returned on a couple of systems where permissions had been adjusted.
The error this time was as follows:
Object enumeration failed
Query: 'SELECT StartMode, State FROM Win32_Service WHERE Name = 'MSSQL$RTC''
Details: The paging file is too small for this operation to complete.
The system had effectively run out of memory to process WMI requests. This ended up being a WMI memory leak issue in Windows Server 2008 and required a hotfix as outlined in the following Microsoft KB article: