If that's the case then hell, I'd rather just pick up the RX or R (since there's no region restriction for CDs) and have a native Turbo Grafx for playing the US HuCards. I wonder if this problem is year specific only plaguing early Duo releases? I have to go home and check the sticker on the bottom of my Duo cause I know the newer/boxed one I have was released/assembled a few years later.
If you can, look up the serial/year sticker on the bottom of your Duo and post the year is says. I'll post mine to see if there's any correlation we can maybe make.