Apparently, some ISP's in the UK are now censoring Wikipedia, since the
Internet Watch Foundation listed a web page to be blocked. You can tell
if you are affected by going to the following url:-
http://en.wikipedia.org/wiki/Virgin_Killer
If you get a 404 pate, you can try the alternate url,
http://en.wikipedia.org/w/index.php?title=Virgin_Killer which has been
reported to work for those affected by the filter.
More information is on the report at
https://bugzilla.wikimedia.org/show_bug.cgi?id=16569.
It is causing problems since when everyone from an ISP gets forced
through a transparent proxy, they become subject to the filters that get
applied to the proxy's address.