Anyone heard of this?

I have a Dreamcast that won't start a game from the GUI - in other words, start the Dreamcast without a disc in, then put a disc in after the GUI is loaded. A normal Dreamcast will say "checking game disc" and then load the game. This particular Dreamcast says that, but then goes back to the GUI.

If I start up the Dreamcast with the game disc in, the game loads fine.

Before you say, just live with it, I'm going to sell this on Ebay or here, and I'd like to be able to say it's in perfect condition...

Thanks!