This is the error that you get when you try to expand the My computer node in COM+ MMC snap in :
An error occurred while processing the last operation.
Error code 80040154 – Class not registered
The event log may contain additional troubleshooting information.
Follow what this link says and you will be back up and running. It is not really necessary to reboot your comptuer as the article says : http://support.microsoft.com/kb/301919/EN-US/