Users cannot Register/Login

I've tried with email activation both on and off.

With email activation off:
1. The user can get to the registration screen.
2. The user can enter their details and hit "register".
3. The user gets a message saying "registration completed, you may now log in."
4. The user does not show up in either the "new users" database nor do they show under "users" in the database.
5. When the user tried to log in, they get "invalid username/password"

With email activation on:
1. Same as above.
2. Same as above.
3. Same as above.
4. User DOES show up in "new users" database while they wait for activation email.
5. Once the user activates the account, the user disappears from the database. They are not in either "users" or "new users"
6. They try to log in, it says "invalid username or password"


I can manually create accounts through the admin cp, so I think it's a problem with the registration.php...