iSight not working

I re-installed OS X on my macbook today, and whenever I fire up Photobooth or any other application it says that an application is already using the iSight so it won't work but this just isn't true - even after I've tried rebooting.

and before you ask, i re-installed the o/s because I deleted too much nifty stuff to get more hard drive space (that I don't even really need)

I had the exact same problem when I reinstalled the OS... I then installed the OS again and it worked fine.... Hope this helped.... :headphone