Likewise, my comments, as usual, were mainly based on my previous errors. As always what Dr Byte says is true.
In my case a complete database export from the old site and then re-import to the new site caused similar symptoms to those you describe. And gave me a 'HUH??' moment. Particularly, when I couldn't log in to admin with the new log in details.
It seemed to make sense when I thought about it. All the configuration for the admin is stored in the database so when I replaced it all the configuration was replaced, effectively reverting the new site to the old site admin configuration. So, for instance, if I overwrite the table 'admin' then all the details of the admin names and their logins will be 'reverted' to the details of the old site.
I would take Dr Byte's advice and work out what exactly the problem is. Are you seeing the new database? Are you seeing the new admin at all?
Also, I kind of agree with his about being loath to mess with those tables. That's why in my case I just rebuilt my admin section by re-entering the values as per my initial advice.