that's odd that you'd get display but no sound. here are a couple things to look at:
-make sure your iPod volume isn't all the way down (it really shouldn't matter but it might)
-I know with the iPod video you have to select "video out" in one of the menus to get it to output video, there may be a similar audio option to get audio signal out from the dock connector rather than the headphone jack, not sure though
Which iPod adapter do you have (there are many and you didn't specify)...do you have the Pioneer CB-100II? or an aftermarket brand? Or are you using the FM transmitter type?
