I've got this too. When the game came back up, after the reset, I came in to find that I had a group invite. I accepted it but it did not disappear, so now I have an invite to this group on my requests page, though the group does seem to have me listed as one of their members.
I'm having the same problem with an invite to Global Chat 2.0, the request remains there and won't allow me to accept or decline it. I'm also getting the server_error popup message.