I guess that is a possibility as it could also fall in line of why it is intermittent, this could be ads poisoning and since the ads would be rotating, you would only get it if there is a poisoned ad displayed at the time you visit the link. Or that avast doesn’t like the ise of the iframe for redirected traffic.

Plus me having AdBlockPlus installed may block any iframe ad content from ad.adperium.com (and why I don’t get any alert), another reason to block ads ;D