If you registered a new user after configuring it for AD/LDAP, then I assumed it registered a user from AD/LDAP.
I suggest go into the database in the mp_Sites table and change the UseLdap field to 0 or false. After updating the data recycle the app pool or touch Web.config to clear the cache.
Then, next time if you want to keep trying ldap, check the box in site settings for "Use Database Authentication With LDAP Fallback"
That way the existing database users will keep working so you can get back in as admin if ldap is not working.