When I cannot login to the ACP, I use Recovery Mode to help disable all third party resources.
If you don't already have a constants.php file, you'll create it and add it to your IPB root folder (where your conf_global.php is at). When you login to the ACP, you should see a message about things being disabled for you. Once complete, you'll remove the constants.php file (or the variable you added to it). Hopefully at that point, you'll have access once again to the ACP.