msn messenger — sign in problem

i m facing a problem in sign in after new install version of msn 7.0. i starts sign in , the the moment it completes it , the window of msn messenger with not sign in indication remains while the whole set up of it gets hang up. my friends c me as sign in but on my pc, i can only c starting window of msn . then i have to end task th exe to close it down. help me please, i hv uninstalland/or repair exe many time but the error is there.