You could try a clean install of msnm:
1. uninstall MSNM
2. reboot
3. remove all folders pointing to msn messenger in programfiles folder
4. remove C:\Documents and Settings\<username>\Application Data\Microsoft\MSN Messenger (by doing this you will loose all custom emotes and backgrounds aswell, you can back them up by using
CE/DP backup wizard wich works with MSNM 7 too even tho it doesn't say so)
If you don't see this folder then you got the folder hidden to make it show go into a folder, in the menu click on "tools" > (folder)options..go to "view"tab and in the list scroll down to hidden files/folders, check to show them and click "ok".
After doing all that reinstall MSN Messenger.