by Justin Hunt.
Sorry, Davo is right. I had the wrong end of the stick on file_prepare_draft_area . You might be better to pursue that route, than the code I sent.
FWIW In answer to your question, if $f is properly set to the stored file that you are copying, yet get_file_info returns null, it is likely a permissions problem. Is the user you are logged in as the user who owns the files?