If your URL is www.mysite.com:

1. Check and see if www.mysite.com is listed under portal aliases for your default portal (eg - portal 0).  If it is listed, remove it.
2. Add www.mysite.com to the portal aliases under the new portal's portal aliases.

Given what I said, you really shouldn't be using Site Templates to move your portal.  It's not the recommended way and many modules don't support the IExportable interface required for this to work.  If you continue doing this, you will break your site and you will not be able to recover your lost data.

The errors you were seeing when doing a database migration were probably related to either a feature set that wasn't installed on the production machine or to SQL security.  I would check to make sure both have the same feature sets (for example, I had used full-text indexing and didn't have that on the production machine) and then check to see if both have the same users.  Then I would check the web.config and make sure the connection string was correct.  If I was still receiving errors, I would check the SQL Server logs and then, finally, come to the forums to see if someone could help.