When a friend or guildmember starts a party, and I attempt to join, I get a message saying "Oops! [Player] is no longer joinable", even though I have my party open to friends and guild. They can only join if I invite them first and they respond to the invite. This works the other way around--I am unable to join my friends parties via the Join option, but only via an invite.
Unable to join parties
Sat, 06/25/2011 - 16:17
I'm getting this too, in the past couple of days. It's a pain in the ass.