I will catalog some techniques for recovering from a completely FUBAR'ed theme. Sometimes when something goes horribly awry with your theme you can no longer log back in and may also run afoul of the too many failed logins problem when the site's scripting is also messed because of a very broken theme. Not a good time. Been there. Done that. Do not want to do it again!
I was attempting to troubleshoot an install and I became locked out. I was trying to change the password through My SQL, but it would not work. What I eventually came to find out was that Drupal 6 and 7 use different password hashing techniques:
I found this great post titled 'Drupal not Sending Email? Let's Debug it! ' on Drupal Connect by Matt Crittenden (see link below) and I am reposting it here with some slight changes so I do not lose it: