So as I said earlier, NLaS was down in the hundreds in Amazon's Kindle store for most of the day. It's still at 230. The odd thing was that my reported sales were less than my usual daily sales (and something like a fourth of yesterday's sales). I wondered about that, but figured that maybe once your book is ranked high, it's harder to knock down.
I went out to dinner, then came back and refreshed the "my reports" page. I was bewildered to find that the usually accurate Amazon had removed quite a few of my sales, and a substantial chunk of royalties. I fired off a note to DTP support, then checked Kindleboards. A lot of other authors were reporting the same problem. Moreover, they were reporting unusually low sales today, too. So at this point I have no idea what my actual sales were like today; it seems likely there's been a problem with DTP all day. I know they're in the process of switching systems, and the general theory is that they may have lost part of their database. I just hope they had it backed up!
Anyway, right now, I honestly have no idea what my sales have been all day. Now that I've gotten used to the obsessive checking of stats, it's a bit odd to be entirely clueless as to sales. I just hope Amazon isn't as clueless as I am on the subject:-).