Migrating hosts --> Can't login to Admin CP
 

I'm in the process of migrating our boards to a new host (Bluehost). I'm unable to login to the Admin CP for the boards on the new host currently, and I get treated to this charming error message and nothing more:

Could not connect to db

I have no clue what's wrong: Did some PHP script testing; credentials are fine, database name is fine (though changed from what it was on the old host), host name is fine (Bluehost says just use "localhost"). I can pull down a list of the tables in the vBulletin database with a simple PHP script, and I've changed everything in config.php to match, so why can't vBulletin run?

I know I need to open up a ticket with vBulletin support, but I'm waiting for Bluehost to tell me how to give vBulletin support access to phpMyAdmin without having to give them access to my entire hosting control panel. Just wondering if anyone has any ideas for things to try or check in the meantime. (File permissions should not be an issue since I spent something on the level of several hours checking to be sure they were accurate.)

(Forgot to add: Our boards are version 3.6.8. Feel free to move the thread if this changes how to approach the problem.)

Please help!