Arboristsite (221,390 Discussions 4,470,092 Messages 54,063 Members) got hacked on VB4 because they had not removed the install folder. The Hack persisted through several re-installs and eventually resulted in them converting to Xenforo.
Google also says the site is clean, so I don't know
I would search the database itself for any references to the apparent malware domain (polarek.pl), see if someone has linked to a picture on that domain or something.
Another scanner says OK, too - http://app.webinspector.com/public/reports/19944954
After just spending 4 hours cleaning up hot linked images that were dead links back to 2008 I am looking for a way to disable future IMG code while preserving any remaining ones. It just makes sense in the long term to host them yourself.