Samsung Galaxy S3 stuck on ATT logo

[AC Question]

I have a Samsung Galaxy S3 (using Straight Talk) that gets stuck on the ATT logo when booting up. I have tried a new battery, and have done a factory reset, but it's still stuck on the ATT logo. When I hook my phone up to my PC using a USB cord, it won't connect. I have Googled the problem and it seems to be common, but after trying all the suggested fixes, nothing works. Please help!