Webcams not responding while video chatting

Whenever I try a video chatting on my Notebook PC then my webcam does not show anything except for a white screen. The condition is normal in the case of photos but the webcam shows unnecessarily white screen with some dark patches on the edge of screen which is very annoying. And next thing is, the white screen shows up only after some seconds of video chatting. I am using HP Pallivian G6 notebook. Please fix this problem I am very annoyed with it.
