Blocked web request to "static-tagr.gd1.mookie1.com/s1/tagr_lib_appnexus_uk_v2_290688457.js" (linked from "www.pistonheads.com/gassing/default.asp") for user **** 'Mal/HTMLGen-A' has been found at this website, reference ID 48326256.
Yes it's Sophos. My companies a Sophos reseller so I know there is the occasional false positive. If it hasn't cleared up tomorrow I will get the admin to report it as a false positive.