I looked throught he manual but could find no trouble shoot help. it was working fine but now I just get a black box if I use video in say skype or if I use photo booth. Both are set with the built in camera as their preference.
Reset SMC. http://support.apple.com/kb/HT3964
Choose the method for:
"Resetting SMC on portables with a battery you should not remove on your own".
Retrieving data ...