There are some other threads about charging issues & compatability with the new ipod touch. As I understand it, a little while back Apple changed the way the ipod charged. They told 3rd party manufactures they needed to change their devices.
The previous ipods continued to work with either method. This time, with the new releases, Apple has inforced the change they asked for a while ago & not all devices work. Some of the sound docks don't even work. I tried a Bose dock & it in the store and it worked but others have a different Bose dock that doesn't work.
I have a newer iHome that works fine, but the cable from the back of my incar stereo does not work. (Sounds like what you have) The ipod actually got very warm when I tried. I have a newer DLO car dock I still have to try. I am hoping it works.
Hope this helps.