The funny thing is, this problem was with this avatar on firestorm, but not with the other avatar. So I am sure, e reinstall wouldn't help. Logged this one in then into the old Phoenix, and there I can open the groups and join them. But if this would be a firestorm-problem, then it should neither work with my other avatar. Very weird. After trying in Phoenix, I logged back in into firestorm, and again, same problem, but only with this account. That is totally weird and frustrating. But thanks again for suggesting some ideas:) If it continues with this one, a clean reinstall certainly wouldn't harm.