Same Problem with Migration Assistant: Leopard to Lion
Had been waiting for the new MBAs and Lion, bought it on day one (and love it, btw) and now I am having the exact same problem, the computers cannot see each other except for a message on the "to" machine which says I need to update MA on the "from" machine. However, the "from" machine is completely up to date.
I am assuming that Apple will eventually (and hopefully soon) release an update for Leopard (10.5.8) that will solve the problem, and I'll probably call them soon. Will update this post if I get some definitive answers. For now, I have connected the two machines using an ethernet cable and ethernet/usb adapter. By turning on file sharing on the old machine, I have been able to grab a few things I am working with at the moment. I might have to start moving applications over this way, too . . .