Drupal 7 is a moving target, and Ubercart 7.x-3.x is going to be keeping up with all the changes in Drupal 7.x-dev

The alpha release was tested against Drupal alpha3 and against -dev as of 14 April. If you want to follow along the best thing to do would be to get Drupal HEAD out of CVS and get Ubercart 7 HEAD out of CVS, then keep them current. That way you won't waste time dealing with bugs that have already been fixed.