Ehhh....in lieu of being able to submit it, if I had to guess and this was my system....I would treat the detection as a false positive, given the various circumstances.
Avast! for Windows has gone wonky at least once these past couple days, returning detections on its own files, that might be what is happening, Avast! detecting a part of itself within the VM, also VM files have been flagged before with odd FPs. Update your definitions (if available), and if that does not clear up the problem, just exclude the VM file/folder from scanning, since Avast! installed within the VM shows clean.
Mind you, that is simply guesswork, and infections are serious business, so if you wanted to be ultra cautious, just delete the VM. Also, if you do not delete it, and the detection persists, someone from Avast! might want a look at that file...it would have to be sent over ftp, but wait till hearing from someone from Avast! before that, as anything sent ftp unsolicited might be lost/ignored.