Shoutbox

Then I would try a clean reinstall... This involves editing your Windows Registry, which you should do carefully, removing an important key can cause your system not to start up anymore...

First, uninstall both MsgPlus and MSN Messenger (back up your MsgPlus settings first if you want, and delete them when the uninstaller asks you if you want to). Restart.
Go to Start > Run, type regedit and press enter. Go to HKEY_CURRENT_USER\SOFTWARE\Microsoft\MSNMessenger, select it and  press the Del key to delete it. Do the same with HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSNMessenger.
If you have Windows 2000 or XP:
Go to Start > Run, type %appdata%\Microsoft and press enter.
If you have Windows 9x:
Go to Start > Run, type X:\WINDOWS\Application Data\Microsoft and press enter (X: is the drive name where you have Windows).
Once you're there, rename or delete the "MSN Messenger" folder.
Delete or rename MsgPlus folder too.

Install MSN Messenger and MsgPlus again. If it still doesn't work, then it could be some other program incompatibility, tell us what you have running.