Originally posted by funksoulbro:

Green Man Gaming is also inaccessible. It works fine in IE and Opera 18, but in Opera 12.16 if I try and log in or if I add something to my basket and try and go to the checkout stage, I got a "403: Forbidden" error.

It wasn't working for me either until I tried enabling 'Send referrer information' in the site preferences. Hope it works for you, too!

EDIT: And disabled Adblock. Having Ghostery still on doesn't seem to matter.

EDIT: I tried with Adblock on again and it worked; I have no idea.