Vista - msn messenger keeps signing me out

if i open a convo with a friend i cant do anything else on the computer
because when i go back to the conversation window it tells me an error has
occured and has to shut down and that if vista can resolve it , it will let
me know, this happens every time i leave this window but i can sign in
properly and i can have one convo as long as i dont do anything else !!!!
otherwise it keeps shutting me down,

can someone please help me as i cant understand it, it has worked fine
before for last 6 months !!!

and ive tried reinstalling it 3 times !!!

thankx drummerhoyle