This is on all browsers I have on my Mac - Chrome, Safari and Firefox. This is real strange as 10 minutes beforehand I could do anything, that was when the forum was running under another domain name.
I have updated the admin area (BTW yes I can login there) with the new URL's etc so that can't be the cause. Anywhere else I should be looking?
EDIT: It is the same error for anything that triggers an overlay, whenever I click anything that does I get the exact same error. HELP!