You have to stop and figure out what changed when it stopped working all of a sudden like that... My guess is that your host probably upgraded their PHP (which turned off Register Globals), or they just shut it off.
So, you should call your variables a little differently now. I can't get your source code because your phps files won't pull up for me, so I don't know what method you are using to submit the variables, so I am going to assume POST for the sake of this:
Where you are looking for some variable passed by your form, you are probably calling them directly like so:
$filename
Well, if you POSTED the variable, you should call it like this now:
$_POST['filename']
This would be the first thing I would look into.