I experienced a simlar problem. A solution that seems to work is to edit mainfile.php back to the original URL, then go in, temporarily disable protector, then clear caches, then reedit mainfile.php to the new URL, then update both the system and protector modules, then reactivate protector.

This was not necessary with 2.3.2b and before, but seems to be so with 2.3.3 (or the new protector that comes with the new 2.3.3). Something seems to not like simply changing the URL via a mainfile.php edit without these steps.