Previous file does not get deleted when a new file is submitted.

I'm assuming there is already an existing image uploaded/submitted in the current node.

If you select a new image and click upload, imagefield updates properly by removing the old file from the DB and filesystem. But if you select a new image but click on the Submit button of the node instead, the new file gets inserted but the old file is still in the DB and filesystem. I'm guessing that by clicking straight at that submit button, the hook does not call imagefield_file_update() at that point of time. I can't figure out where, else I'd submit a patch.