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