Hi there,
Yeah, that Google Chrome is a bit of a PITA for this kind of stuff...
The problem in this case is with the avatar folder. That's why you only get this warning when you read threads (when you start to see avatars basically). It takes a very long time for Google to change the sites ratings (you will see, if you look in the error details, that Google said the website is clean.... Go figure)
Anyway, no worries, website / forum is "clean", Db tables, scripts etc are scanned live, and site advisor check the site on a daily basis (from work)