Did you actually check everything or just read the list? For instance, did you open the player and remove the disk tray and wiggle the connector and look closely to make absolutely sure it wasn't the IDE header solder joint problem? Are you certain you've never exposed the disk drives to extreme temperatures? (etc.)

If so, and if you're really sure that nothing else on the list is the culprit, then yeah, I'd say that an actual disk drive failure is a serious possibility.