Either my computer is infected and they got the ftp password, they was a hole in the board software/server software required for the board to run, or both. It seems that quite a number of sites are infected currently, and the infection is proving difficult to remove. I've already removed it from a good dozen files, and it was put back in again before I was done fixing the last batch.
The current one, .c00om, is a little tougher than the last one. The go00ogle one was easier by far. I've been downloading all umpteen million files the board runs from and searching all the text in them for iframe or google. The code for it adds the zeroes to the address on the loaded page, which means I can't search for go00gle. Same with .c00om, except I can't just remove every mention of .com without breaking everything.