I had a minor problem upgrading Protector from 2.40RC2 to 2.52 on XOOPS 2.2.

After putting the 2.52 files in place, I wasn't able to access the XOOPS admin page to upgrade the module; I got logged out of XOOPS whenever I tried it.

I solved the problem by manually disabling the Protector module in the database (in the xoops_config table, change global_disabled to "1") using phpMyAdmin. Then I was able to access the admin page, upgrade the module, and re-enable the module.

Editing mainfile.php to temporarily remove the precheck/postcheck would probably have worked too.

Just a heads up for anyone who runs into the same problem. You may want to disable the Protector module before attempting to upgrade it.