Hi ignacio,
Thank you for the reply. Before I read it I actually did what you suggested, and got things working. In the database, I manually added a company (with id 1, to table companies), added a user assigned to that company (with id 1, to table users), added an Administrator group (with id 10000000, to table groups), and added my user to that group (in table group_users).
I tried using id 1 for the Administrator group, but it didn't work -- when I logged in, my user had no administrative rights (no link to Administration). I tried 10000000, and that worked. Haven't tried any other values, so I'm not sure if any others would work.
I had to click the "forgot password" link on the login page initially, as I had no idea what my password was set to in the database (as it is encrypted). I got an e-mail with the reset password, and I was good to go.
Hope this might help anyone else with issues.