the isight on my black macbook is not working with yahoo messenger and skype, but its working with photo booth though. when i click on the webcam icon on my yahoo messenger window, the isight starts up but it doesnt send a request or invite to view the webcam. I also encountered a problem with regards to viewing the webcam from othre computers. when i accept their invite, the window opens up but doesn't proceed, it only shows a blank screen.

please help. thanks.