Biult in Webcam problem

Hi, I'm using an HP Pavillion notebook. I don't have any problem using my yahoo messenger version 8.1 before until last night when I used my built in webcam on Yahoo messenger. It crashes when i invite someone to view my webcam. I also have problems with the call function because I can't call nor receive a call from someone. I tried uninstalling the yahoo messenger and reinstalling it but nothing happened. Please help and thanks for taking time to answer my query.