Sorry that this is so short -- I'll update with more if I can get some links and more information.
I'm listening to Rachel Maddow on Air America right now (It's not Rachel, though, David Bender is substituting for her for part of the show) and a woman named Michelle called in and said when she was driving to Saddleback, they were pulled over because they were too close to the McCain motorcade, and that the motorcade got to the church before it started -- which may mean that the "McCain wasn't even there for the first half hour" statement was a lie.
She said she has a video with a time stamp and will be posting it on YouTube -- she didn't realize this was an issue until she was listening to the show. I think she also said she has toll receipts and other proof that she was where she said she was at that time.