Sometime around July 4th the website got attacked and a virus installed in its files. It is identical to a virus attack on one of my other websites earlier this year. Knowing how it worked, it was fairly easy to remove. I firmly believe this originated on my host's end, and will alert them to yet another case and let them track down the cause.
At the moment, as near as I can tell the site is "clean". Please let me know if you run across anything that appears suspicious.