I have never encountered a "not fully loaded" error, but one of the following will usually correct camera problems:
• 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, (the "reset" suggested there
often restores normal function,) continue.
(Apple has changed the built-in camera's name on newer Macs from "iSight" to "FaceTime" and then to "FaceTime HD." Regardless of the name of your built-in camera, the same info and troubleshooting applies.)
• Use your Mac's Disk Utility to repair permissions and then
download and apply the latest Combo Update, for Mac OS 10.8,
the current one is at: http://support.apple.com/kb/DL1581
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 the camera. For hardware help, contact an Apple-Authorized Service Provider for service.