Not if he's using a MD2. Probably a bad or dirty cart. My guess would be it's trying to play the 'off-road driving' sound and is not able to. I've heard a lot of reports of flaky VR carts, so it wouldn't surprise me if the cart was bad.
edit - oh wait, I didn't see keropi's other post. Hmm, that's interesting, I didn't know they made any 'incompatible' megadrives. What country is the unit from?