londrum - 9:27 am on Aug 27, 2010 (gmt 0)
wiping individual sites isn't going to help, i don't think. if multiple sites are infected on the same server then it's likely going to be something installed on the server itself, which then filters down to everything below it. wiping the sites isn't going to stop it if you leave the original there.
look for something untoward in the folders above where the sites are stored -- and then wipe the individual sites
but... you also need to find out how it got there, or it might happen all over again.