Amy-AM-30min-Raspberry Pi Reboot Troubles

During the class tutorial, my Raspberry Pi hung when I changed the configurations to enable the camera. From that point, my Raspberry Pi hung when it reached "Starting plymouth reboot screen..." I tried restarting the Raspberry Pi at least 10 times, but go the same result. I also noticed that the heat sink was warm/hot when I touched it, so that may have cause in the rebooting troubles. I searched on Google for Raspberry Pi reboot hang fixes, but most of the forums weren't much help.

Links:
How to fix Raspberry Pi boot problems
Raspbian hangs on reboot