My Sony CD player rechargeable batteries won't... (by 3 users)

I have a 5-year old DEJ100 Sony CD player, whose rechargeable gumstick batteries will no longer re-charge. I've tried cleaning the terminals on the recharger cradle and cd player and changing the batteries, to no avail. When I try re-charging, the "charging indicator" red light comes on for about 5 seconds, then shuts off. The CD player still works if I use AC adapter as power source. Is there anything else I should check before calling it quits and upgrading (reluctantly) to an ipod? Thank you!