Unfortunately, unless the founder comes back from retirement, it looks like this group is gone for good. You may have to create a new one. Make sure that when you do, you set the admin (and member, if you want extra security) permissions to "Subject to Vote" or "Are Not Allowed" so that you can stop more cases of this happening. Warn the other groups you are in to do the same as well.
I'd also suggest you join or watch the NoMoreHackers group. It monitors the newest sockpuppet accounts of the troll and the groups they have attacked.
www.deviantart.com/nomorehacke…