No users inculding the admin and host can login to our site after an upgrade. Here is the history of this account;

We were running DNN 3.1.1, and all users could login (host/admin inculded)
We upgrade the site using the DNN 3.3.7 upgrade install
Site shows in the copyright area at the top DNN 3.3.7
Now no one can login.

I have no idea where the passwords would be loacted in the SQL table, but I thought they would be in the Users Table, which I don't see them. So, I looked in the aspnet_Membership table and see user IDs and passwords, but they seem to be encrypted. I do remember placing a value in the encription box when 1st setting this site up, and I do remember what that value is...

My main question is how can I (admin/host) now login to our site?

When you do an upgrade the new version comes with release.config and development.confog but now web.config.  The reason for this is so that you dont accidentally wipe your web.config file which ahs the machine Keys in it for your site.  You need to transfer the machine key section from your origianl site to your new web.confog file so that passwords can be validated and decrypted.  If you have lost these you need to regenerate the hsot and admin passwords exteranlly using the encryption you have set in the config file and update the db.