I have had some problems with the "purchased" not "ticketed" thing with Amex. Both times it was because Amex put a hold on my account and I didn't know about it. One time it was because of my Bulgarian and Serbian charges which instigated a hold; another, I purchased 8 tickets over a day or two, and they held only on the last couple. I have a platinum card fwiw. Calls from and to Amex cleared it up, but I had AA contact me after a couple of days to tell me there was a problem with the card, which was declined the first time and apparently not run again.