MMC cannot open the file C:\WINDOWS\system32\gpmc.msc
If you are receiving the following error:
Simply browse to the following directory, replacing *User_Name* with the affected users sAMAccountName:
C:\Documents and Settings\*User_Name*\Application Data\Microsoft\MMC
Then delete the ‘gpmc’ file. This will reset the gpmc console to its original configuration, but allow you to use it!