Web site blocking software. It doesn't like PeopleWhoRefactorWiki, those WhoRes.
I was once told a story about similar software causing problems with HTTP tunneling and code. -- ErikMeade
It is always fascinating, how these programs go havoc. The grand prize in the FoilTheFiltersContest? (http://dfn.org/focus/censor/contest.htm) went to Carroll High School. You could not access their own web site from their school library, since the name of the school contains the word 'high'.