I had used (can't remember his name) Galaxy S3 Toolkit to root the phone. Interestingly, Root Checker said I was rooted, but Titanium Backup wouldn't install... It said I needed root access... Hmmm.... Later when I went to unroot using the same S3 Toolkit, I did something wrong. The phone would boot but stick at tiny little letters in the upper left of the screen that I *think* said recover. I messaged the developer of the Toolkit and he sent me a link to download the original AT&T stock ROM. He told me how to use Odin and check the PDA box. I did it and it fixed my phone.
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