The documentation does not indicate whether or not there is a difference setting up the file upload for an insert page or an update page. The "default" file field on the second page of DFP2 does not seem to retain the data. I place the name of the hidden image field using the lightning bolt icon like I did with DFP1, it accepts it, but doesn't write it to the code and when I go back again it is gone. the "default" field is not even mentioned in the online help files.
I was able to get it to write the filename to the database once by deleting the server behavior (DFP1) and redoing it in DFP2. Now for some reason it doesn't work at all, the file gets uploaded but the information is not written to the database.