Webcam problem on windows live messenger 2009

on windows live messenger 2009 my webcam use to work perfectly fine but now everytime i try to use it when the other contact accepts it loads for a while then said 'webcam seession has ended' this happens when i accept the other contacts webcam aswell. ive tried uninstalling and reinstalling the messenger and ive got all the lastest visual drivers for the laptop (dell studio xps 16) please help