If you need to manually disable a module you can do so in the database. Before you start, do a mysqldump (or export) of your Drupal db to a local file in case things go wrong and you need to roll back.
Accessing MySQL
In order to perform these commands one must have access and proper permissions to execute MySQL commands. These commands can be executed with GUI like phpMyAdmin, or just the MySQL command line interface.
phpMyAdmin
To disable a module via phpMyAdmin you must login to phpMyAdmin. Then you must locate the database where Drupal is installed. Once you have done so look for the "system" table. Click and open it. Click to browse the table. Find the record for the module that is causing the problems and select the edit function. Set the status to "0" and save.
MySQL command line
To disable a module using the MySQL command line, run the following SELECT to look at the state of your data before the change. This will help you to find the full name of the module too.
MySQL Commands
See all the modules enabled:
SELECT name,status FROM system WHERE type='module';
See if a particular module is enabled:
SELECT name,status FROM system WHERE name='module_name';
Disable your module, set the status to 0 for the module name that you want to disable.