Umm... My best guess would be... just exit the window, or something... could be some sort of adware or spyware or something though... Might wanna run a scan on your system.
Edit:... Figure I should probably tell you I'm not sure what NCsoft is... I'll google it
Edit again:... I looked it up on google... all I got was some game site... had nothing to do with MSN Messenger at all that I saw.... SO! I'm sticking with my "run a scan" reccomendation... If you don't find anything with a spyware scan try a virus scan too.