ChatRooms gone after upgrade 3.8.0 -> 3.9.1

Hi,

i recently upgraded a 3.8.0 installation to 3.9.1

The upgrade went smooth, but I lost all existing chatrooms, which is a bit unhandy to be honest.

The rooms are still in the ofMucRoom table, but the list in ther webinterface is empty.

Any hint on how to get the rooms back?

Thank you.