Isight Issues
There is indeed a issue regarding isight on some (but not all) macintoshes for example MacBook Pro. isite related applications like Photobooth will get a message as follows;
" Photo Booth cannot open because no camera is attached or the camera is in use by another application"
But this problem is a iSite issue so Ichat and Imovie which also uses iSite will have the same error message.
THIS IS NOT A HARDWARE ISSUE
You can confirm this by getting your "For Mac Computers Mac OS X Install Disc 1" and insert into your disk drive. Reboot an hold down the D key as the computer starts up. This will you the option to do a Hardware test. I am pretty sure your test will be successful. This test will help you determine whether the issue is software or hardware related.
THIS IS A SYSTEM PROBLEM
This is not a profile or application issue. If you reset the PROM and reboot 3 times with this command, it sometimes solves system issues. However, I am sad to say it will not solve this one.
REINSTALL OS
Apple is being quiet about this issue. That is to say, their engineers have not informed Support Helpdesk about this issue regarding isite so your phone calls to support will probably not do much. You will need to do a re-install. The good news is you will not need to do a CLEAN install but just a system archive overwrite install. It shouldn't take over 30 minutes. Before you do your updates, launch photobooth and it should work. Then, do your updates and then try again.
Log your actions
If you still have issues, be sure you log your actions and report to Apple because they need to address this.
-SENJU