Group invite bugs?

Daemons_Bane

So, while running around exploring, I'm asked if I want to fill a dps role in a guild dungeon run.. I accept and they send me the invite, but when I accept it, I am told the group is full.. I ask them if they had found another, but the spot is free, I just can't accept it for some reason.. I am level 50, CP 125, so that should be ok.. Can anyone tell me if there is a fix to this?