Did you also check more than one user account to eliminate possible user-specific problems? Do NOT use the "Guest" account for this test. If you do not have more than one user account for the testing, create a new one now. If you need help, here's how to do it in your Mac OS:
• Then, if you have not already done so, restart Mac and
try again. If the iSight still does not work, continue.
• If Apple's http://support.apple.com/kb/HT2090
suggestions do not help you, (are you certain that you
used the correct "reset" procedure?), yours is most likely a
hardware problem that will require a professional fix.
Unless you have a current backup, make one now.
Then use the final "Troubleshooting" suggestion:
"... contact Apple or an Apple-Authorized Service Provider for service."
• If you want to try one more thing on your own first,
use Disk Utility to repair permissions. Then
download and apply the latest Combo Update for
your OS. Currently, the latest SL Combo is here:
• Repair permissions again immediately following the system restart
that completes the Combo update.
Properly applying the Combo version of updates can sometimes correct software problems, but, if your trouble is caused by a hardware problem, there are no user serviceable parts of iSight. Have your Mac professionally serviced.
The only other user action I could sugget is to completely reinstall your Mac OS. If none of these suggestions resolve your trouble, I think you will need an Apple-Authorized Service Provider to fix your cam.