Uh Oh. Help!!!

I was able to get it working by opening a backup of the project I made a few days ago. I had to re-do quite a bit, and I deleted all files from the server and from the output folder, but after I FTP'd the new build to the server, all is working.
Now, I need to add a field to the user registration page that new users use to sign up. The existing registration box simply asks for a username, password, verify password, email and a captcha. Now I need to add one more field after-the-fact. What do I have to do to make this work? I am wondering if the meltdown happened because I added the new field to one table, but since those tables were auto-generated, I messed with things????? I am not sure if I am wrong, but if i'm not, how do I re-do the user login settings/tables to make this new field work? The new field needs to be a drop down.

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Error message suggests that connection parameters are incorrect. Make sure MySQL server address, username, password and database name are correct. Connection parameters can be found in include/dbcommon.php file.