Sony CD Clock Radio Not Supported by iPhone?

Hello. I have a Sony CD Clock Radio for iPod & iPhone (FM/AM CD Clock Radio ICF-CD3iP) that I use with my iPhone 3G. The iPhone 3G is one of the products compatible with the clock's docking station; at least, that's what it says in the manual.

Unfortunately, I've been sporadically told that "this accessory" doesn't support iPhone. The clock is unable to broadcast or operate the iPod app any time that message comes up, and I can never predict when it will happen. Does anyone know how I can stop this happening?