i Sight vanished!

[Jobaghalford]

Dizzy mother of two exasperated . Since boyfriend, trying to be helpful, re installed the operating system 10-4-11 my i Sight camera does not work with Photo Booth, or Skype. It says:

Make sure your digital video camera is properly attached and turned on. If you are using the camera with another application, close that application before trying to open Photo Booth again.

I am not using the iSight camera with another application!!

HELP!

 

[.Max.]

What model iMac do you have?

 

[Jobaghalford]

Tempted to put 'a white one' but that would be silly. This any help?

Model Name: iMac
Model Identifier: iMac4,2
Processor Name: Intel Core Duo
Processor Speed: 1.83 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache (per processor): 2 MB
Memory: 512 MB
Bus Speed: 667 MHz
Boot ROM Version: IM42.0071.B03
SMC Version: 1.6f0
Serial Number: CK6400FCWD4