php form problem

PHP was upgraded from 4.1.2 to 4.2.3 recently. I found out that the one of my problems was related to register_globals being turned off. I fixed that, but now theres another, possibly related problem. A former employee wrote a page with a form on it. The form is entirely php. After you click submit, it should redirect to a thankyou page. Well, it doesn't. It just goes to a plain white screen and the message gets lost. I don't know what I'm missing. I have not modified the form page. I'm guessing something inside php.ini needs to be changed? Any suggestions? Aaron