I have a XOOPS site running 2.0.17 that's been working fine for some time. Suddenly, in the admin, every time I try to do anything other than view the main admin page, I get taken to a blank page. The page name is session_confirm.php

No files have been changed in a year, so it's not something the client accidentally did, and the server is still running PHP4, so I don't think anything has changed there.

Any ideas how to fix this?

THanks!