Welcome rodrigo.
You have done all the right things. Here are the other things you can do.
(1) If you have not already done so, restart Mac and try again.
If the iSight still does not work, and if you are convinced that none of Apple's suggestions from http://support.apple.com/kb/HT2090 help you, (for example, 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."
(2) 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: http://support.apple.com/kb/DL1399
Repair permissions again immediately following the system restart that completes the Combo update.
Properly applying the Combo version of updates can sometimes correct problems with software, but hardware problems require help from an Apple technician because there are no user serviceable parts for iSight.
Message was edited by: EZ Jim