My problem is a little different than Waz’s, because I’m only missing one page in google.
But it seemed to happen at about the same time – last weekend. Must have been an update.
Edited to say: I just did some more thorough searches, and apparently the page isn’t entirely missing, it’s just been completely knocked out for the search phrases it was in the top 10 for. For instance, I type in the key phrase, and then do a “search within results” for the url, and it isn’t found at all.
So I guess my question is, how does a page that was in the top 10 not just lose it’s place, but completely disappear from the SERPS for that particuar key phrase.