Try to contact the network admin, and request that this website be added to a safe list. Back when I was an admin, I found that many of the software apps used to control web access have some strange presets that can be tweaked- aopa.org was blocked as an "advocacy" website, anything with more than one 'X' in the URL was blocked, etc so I doubt you would be the only one asking for a site to be unblocked. Most of the companies I worked for installed it to protect themselves, not to police their employees. In my experience most of the anonymous and web redirector sites are blocked as a default as well.