Shoutbox

I had a problem kind of the same, problem was i had another add on installed (rubbish one ) and it was clashing with Plus! so everytime i started msn, it crashed and the icon dissapeared when i hovered over it.

Basically my advice is check which add - ons you have installed or any programs which run in the background (maybe posting a list of your programs from task manager?) and un installing anything you dont use or any add ons you think may be interfering with Plus!