My site contains porn?

Don't get shocked or excited! I went to look at my site at the library yesterday and found that it was blocked. This is the first time that I am aware of that my site has made the filtering engines and been classified. Apparently it was blocked as it is on a server that hosts pornography or free sites. I know for a fact that it doesn't host free pages and there may be some sites on the server that have adult content. However, blocking by ip address seems pretty drastic as using ip to get to the server fails as it relies on the hostheaders to direct you to the appropriate virtual server/directory on the machine - instead you get a "no website exists at this site" message.
I've contacted the library and SecureComputing.com who make the filter to see if I can be removed. (The library assistant didn't have the correct password to temporarily override the filter when I asked)