I've had a book stuck in "publishing" mode for days now. It normally takes roughly a day at the most. I've uploaded a couple of edited versions of my books this week due to the linking TOC's experiment so I've seen firsthand how messed up DTP is this week. One of my books was done obscenely fast while the other is still languishing away yet people can buy the latest version. Makes no sense.
Aside from that, lots of writers have noticed their sales suddenly stopping or worse, losing sales altogether. I read somewhere that Amazon are working on updates to the DTP so it could be that. Hopefully it isn't a total database failure and everyone gets their sales (and earnings) back. I wouldn't worry too much about it. Amazon tend to be on top of customer service so I'm sure keeping everyone happy is a priority for them. Especially when all those writers are earning them a small fortune. :)