I have been doing the same thing with the wifes' truck.

I tried to duplicate this procedure on the home stereo.
I'm coming out of the Treo with a 2.5mm adapter to 3.5mm adapter that goes onto a RCA type jack that splits into 2 cords and then goes into the "Phono" inputs on the stereo. I think there are too many connections involved and after reading this I realize that I am using very old adapters and that is probably the "glitch" I have been experiencing.
Back to Radio Shack for "new" stuff soon..........