When I logged on today I noticed that the grouping section of the social panel was full of what I call “phantom” groups. They all look like they’re empty. The way I fixed this was first to make sure the social panel was closed. Second type /who in the chat box. This will manually load the who panel. Once the who panel has loaded all the characters online the grouping tab should populate as well when you click over to it.
I don’t think this issue is affecting everyone but if it is for you hopefully this workaround will fix it until the devs come up with a permanent fix.