Ran into a problem where WMI stopped responding on a Windows 2008 R2 server which we use to host a Primary Site server. 
Applied these two hotfixes on the Windows 2008 R2 server which are both related to WMI memory leaks, and now the system is running as a dream!

KB981314 - The “Win32_Service” WMI class leaks memory in Windows Server 2008 R2 and in Windows 7

KB977357 – A memory leak issue occurs in the Windows Management Instrumentation service on a computer that is running Windows Server 2008 R2 or Windows 7