You guys posted this problem back in March of 04.
I just starting getting same problem today.
Just so happens that I McAfee's ran this morning and cleaned up the registry and now MDT will not run. Getting the same 'CommCntrClientSink' error. I even checked Inventor and it is running fine.
My wife is now making the 50 minute drive to bring me my install CD's so I can correct the registry entries.
I am sure glad that these older message like yours stick around here for a while.
FYI, I am using,
XP Pro (service pack 2)
This is a Registry error. Registry cleaners cause it. You do not have to reinstall autocad 2007. You can if you want but you only have a limited amout of times you can install or reinstall the program. It is better when you get this error to go into c:/programfiles/autocad 2007 and if the folders for the registry backup and open them and merge the backups back to you computer registry