I've been through the UC installation and can find absolutely no evidence of tampering. None of the files, other than the database and the cache, have been updated recently and there is no evidence either in the access log of the forum itself, or of the web space generally of any unusual activity. No file permissions have been changed. The SQL database and the cache change dynamically with the use of the forum and I can't check them for hacking, but I have run the recommended integrity check on the database and it passed with no comment.
I don't run Kaspersky myself, so I can't replicate the symptoms, but I did access the forum using IE (I normally use Firefox) with Google search enabled and nothing untoward occurred.
I'm at a loss therefore. I don't know if that's enough reassurance, but there's no more that I can do at this stage without any more symptoms to guide me.