I was originally on this flight. As soon as I heard there was an issue, I went straight to the Gate 31 agent and she was able to rebook me on UA900 (was going to SFO anyway). Based on the chatter happening behind the desk, I could infer that it was going to be a while for them to fix (they were told to move passengers if they asked).

As UA900 taxied away from Gate 32, I saw the 763 starboard engine covers open. Not good. When I landed at SFO, I heard it was canceled. I hope everything works out.

Moral of the story - as soon as you hear there's an issue, don't wait....