The beta has a known issue where you should *not* specify the persistence option while making a USB stick.
If that doesn't help I think I saw a thread with similar subject as this email at ubuntuforums.org maverick section here: http://ubuntuforums.org/forumdisplay.php?f=385 -- ubuntu-in mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-in
