I receive this above error very frequently - it happens several times a minute and I have to refresh repeatedly for it to eventually appear. The strange thing is, only forums seem to be affected by it. The only forums I do not get the error on are on Something Awful. OcUK, Beyond3d, NeoGAF, etc all get it, be it vbulletin or phpbb.
Other sites that aren't forums such as BBC news, Eurogamer, Facebook, Grooveshark and HSBC are completely fine and load instantly without any error.
What could be causing the issue?