I dont think this is the worst call ever, but the call that came to mind when I read this thread was Kiffin against UCLA. I know we didnt have a confident QB at the time, but at least with him rolling out it was 50-50. With time ticking away another play up the middle was not going anywhere, and eventually cost us the game.
If were talking strictly UT games, then I would have to agree. The worst call I've ever seen in CFB was the 5th down that gave Colorado the win, I believe it was over Missouri, back in 1990.
I'm going with the second one, just because I wasn't old enough to see the first one. Ohio State fans still swear it was pass interference...Yeah, that Colorado game would get my vote... although the pass interference call in the Miami/OSU game was pretty bad too and changed the national championship.