Well you should be able to get the latest MyBB forum to work with Mysidia by simple edits as proposed by Kyttias:
http://mysidiaadoptables.com/forum/p...php?issueid=52
I think your problem is more about the fact that you already have users on the site or forum prior to integration, which will cause it to fail. The integration script only works with fresh installation of both adoptables site and forum script.