it must be one of the ads if you grepped the files and there is nothing, or its encoded, I would run maldetect on the docroot just to be sure. I am not getting alerted today. I don't see it in the code and didn't see it when I wrote this post and while I was getting the warning unless it was an include or something encoded. I did see it on the index pages also so its definitly not someones sig or avatar. (which can be humerous sometimes I get these report on forums sites on server I admin and the stupidest avatars are infected, I get to tell the client "The problem here is Wayne and Garth, yes the Waynes World Avatar Bob is using..its infected..")..Anyway hopefully I start getting it at work(although I try not to visit this site at work) and I will run firebug on it and see if I can figure it out but looks like you guys got it fixed.
At other posts: Yes malware can effect mac and yes also 486's lol