If someone sends you a request (in this case was Checkers) and you have the Messenger Plus! Preferences window open it goes nuts until you close the Preferences window.

Thanks for reporting ecko (didn't know you were using Plus! ). I considered this to be a minor problem before but as you're more and more to report this limitation, I'll dosomethign about it inthe next version (this is caused by the fact that Alt+X shortcuts are automatically routed to any opened dialog window and Plus! is just trying too much, hoping it will work).