Greetings EVa,
I don't believe this is directly related to MSN Messenger itself as CC3260MT.DLL appears to
connected to the Borland C++ compiler (MSN Messenger is compiled using Microsoft Visual C++).
As far as I know Plus! isn't compiled with Borland either, so I'm not quite sure why you are
seeing this message (unless you've installed some other Messenger utilities).
I tried some quick searches on the web for a copy, but couldn't find anything, so if it's
actually missing, you'll need to try and find the culprit and reinstall it.