There's a table for fast word searches that had a bad index, then the whole table got corrupted. Since it doesn't make much sense to take a very old dump from months ago, I just dropped and recreated the table, and rebuilt indices from scratch. This may mean word searches are very slow as the table gets repopulated, but I think we're in the clear (for now, knocking on wood). Been a while since I did any DBA "heavy lifting". I may have missed things so if you see anything weird, try to describe the problem in detail and I'll look into it. Sorry for the slow response...it took a few hours of trying a bunch of different things first. Next time it'll be easier.
The dump I took today included recent posts, so we didn't lose the actual post data, just the search index. That'll slowly grow as new posts occur. I'm also not sure if searches on old posts will work properly (I think the search will rebuild on the fly...will try this with something from a month or two ago to see if it gets found).
[update] yeah...
old posts don't get found since the search index is all new now...will have to see how to fix this...might take some heavy scripting
