Two users (dolly and and nai) have reported on Twatter
12 that the forum software is preventing them from posting because it detects a virus. Whether this is an issue with their browser, a post they are quoting or their OS is unclear but nai has reported a fresh AV scan
3 does not report any issues and he was then able to post, but ironically when he tried to post about this issue it recurred, hence my reporting of the issue.
Can't offer any insight, not had that problem myself and no idea of browsers/OSs being used, but it prevents people from posting/participating in the forum so I felt it worth notifying site admins about.