I got this ‘Invalid class’ error when querying disk performance data:

Win32_PerfFormattedData_PerfDisk_LogicalDisk

The server was running Windows 2003 R2 Std x64 SP2, so I used this article to ‘detect and repair a corrupted WMI Repository’:

rundll32 wbemupgd, RepairWMISetup

Well, it did not work for some reason. A little more googling led me to a blog, where Mike (the author) suggested two additional actions:

1. First

   winmgmt /resyncperf
   

2. Then

   winmgmt /clearadap 
   

Just executing (1) did not solve the problem for me, while doing (2) after that worked perfectly.

Perhaps, both of them were needed to succeed. Anyway, thanks Mike!