It means you should use MSN Messenger 6.2. MSN Messenger 7.0 beta and especially the leaked out 7.0.0604 build (which I think you are using) is not ment for people that just want to have fun with it but for official beta testers that can write proper bug reports to help Microsoft making it error free.

Please check your computer for viruses. Read more in the other topic.
Also make sure you have the latest Windows updates and patches: http://www.windowsupdate.com

Good luck and it would be nice if you could stay with one topic 😀

I’ve got the newly released official (not beta) version of MSN Messenger 7.0, but everytime I shut it down I get the same error message. Anybody got a clue why?