There is a problem with the 10.5 (Leopard) version of the Macintosh OS that does not upload files to the Certificate Creator. Apple has released an update, 10.5.1 that addresses this issue.
Not all users will run into this, only Mac users that are running the initial release 10.5 and have Flash Player 9 installed (users with Flash Player 7 or 8 won't have this issue). It is recommended that all Deluxe members running Leopard upgrade to 10.5.1.
Basically what is happening when a Deluxe member is logged in and attempts to upload their own image to use with a certificate the file transfer never completes and there is no indication that the transfer was successful or not. The fix is to update to 10.5.1.