17 Apr 07 Getting the error “MMC has detected an error in snap-in”?

http://support.microsoft.com/kb/915797

Microsoft Management Console
Solution: If you start certain snap-ins for Microsoft Management Console 3.0 and then subsequently uninstall Windows Server 2003 SP2, you may not be able to start some or all of the snap-ins in Microsoft Management Console 2.0 afterwards. If this occurs, remove all the files in the %APPDATA%\Microsoft\MMC\ folder.

Getting the error “MMC has detected an error in snap-in”?
After you install Windows 2003 Service Pack 2 or the SBS 2003 R2 Technologies, you might start seeing some MMC snap-ins displaying an error similar to this:

The source of the problem is that the snap-in is not fully compatible with MMC 3.0, and you most likely have already realized that both Windows 2003 Service Pack 2 and the SBS 2003 R2 Technologies install MMC 3.0.
These are some of the components that you might encounter this problem with:
* Health Monitor MMC
Solution: Choose “Continue running and ignore errors with this snap-in for the rest of the session” and KB915797
* ISA 2004
Solution: Install ISA 2004 SP2 and KB930414
* POP3 Connector
Solution: Install KB921096
* Group Policy Editor Tool
Solution: Solved in Windows 2003 SP2. See KB915797
* SQL Server 2000 Analysis Services
Solution: Choose “Continue running and ignore errors with this snap-in for the rest of the session”. See KB915091