Why is my Samsung Galaxy S3 stuck on the boot screen?

[AC Question]

I just tried installing the new update for the stagefright fix on my S3, and the installation failed. I thought this was strange, but I just tried rebooting. I get the "Error!" from the Android. Every time I try to reboot from the recovery menu, the little Android says error and the phone resets. I've already tried clearing cache and performing a factory reset, and the phone still won't go past the Galaxy S3 screen. If anyone could assist me with this it'd be great.