Contact your IT department, they are geeks and will sort it out surely.
The category block is likely mandatory. Some things are up to local IT, and some are decided by NETWARCOM. If vendors categorize the site properly, the issue goes away.
The product formerly known as Blue Coat ProxySG (now Symantec ASG) is the most likely culprit. The warning page may or may not identify the proxy software, though.
FWIW, I know Blue Coat was wrong last week, and I submitted a request for review. (Takes all of two minutes on their site
.) Their info is better now, but some people don't download and approve WebPulse data daily.
If the site is using a different proxy, a review request will have to be submitted to the relevant vendor.