I don't think this has anything to do with msg plus!
make sure to check your firewalls, and antiviruses,
also, if this doesn't work, try running MSN Messenger without Plus!
the fact that the messages won't be sent can proove you that Msg Plus! Has nothing to do with it.
now if you have no firewalls/antiviruses, or that they're all shutdown and that you're still experiencing the same problem, then try using WebMessenger,
http://webmessenger.msn.com
and post back, I'll try to get in contact with some1 who knows more than me to help you
/ 
