I have happily been creating rooms via the XMPP framework for iOS for a couple of months. I installed the lastest openfire version 3.9.3 and while I can create a room either via my own config or just reflecting back the default room config as usual, invited users other than the owner/creator are now getting a "406 Modfiy not-acceptable" when they try and send a message after entering the room.
The only way around this is to adjust the room settings on the server and save the changes. In fact just "save changes" without changes to any room options will also fix the problem.