Shoutbox

I think you should know that Windows Messenger isn't officially supported by Plus! and there has been problems with it's compatibility in the past...After all Messenger Plus! is designed for MSN Messenger
There is a chance that installing Windows Messenger 5.0 may resolve the issue (click here to download)...
But I'd advise you used MSN Messenger itself, it does have more features for the home user but not able to connect to the communications service and Microsoft Exchange Instant Messaging (if you don't know of that you don't probably use it)...
MSN Messenger can be downloaded at http://messenger.msn.com