Well, I've managed to break drupal already.
It's being a royal pain in the ass, and in my frustration I managed to delete some data that obviously shouldn't have been deleted, so I've had to effectively start again from scratch.
This is obivously going to take a little time, so please be patient. I will of course, provide more updates as they become available.
If your user account doesn't work, then try using the password reset function - the database rebuild probably regenerated the password salts or something stupid like that.