I got my udid registered, downloaded a copy of iTunes 10.5 beta 3 and iOS 5 beta 3 for the iPhone 3GS. I alt-clicked restore and selected the beta update, and after iTunes says "verifying with apple..." and error message comes up, "The iPhone "iPhone" cannot be restored because of an unknown error. (20)". I have looked for a solution to this problem but I can't seem to find one that works for me. I'm on a new MacBook Pro 15 inch with Lion.