Not sure what the contents of those .php files are, but I bet it's because you have some missing variable values. If your .php files pass (via GET or POST) variables to another page, you cannot refer to them directly, as of 4.2, because register_globals is now set to "off". If you have a LOT of .php files, I recommend as a short term solution to edit your php.ini file and set register_globals = "on."
HOWEVER
As a permanent (and more robust) solution, you should edit your .php files and fix your variables.
For example, if you had "&name=fred" in your url, you used to access it with:
$name
Now, you need to add this to your .php file so that it will work:
$name = $_GET['name'];
If you passed variables with POST, then use:
$name = &_POST['name'];
If register_globals is not the culprit, then I'm not sure what the problem is.
