i'm using the newest Sprint ROM. i posted in this thread at least once (and a few others) about the audio not working. someone posted (also possibly in this thread) that a quick solution to the problem is to slowly plug in first only the adapter, with nothing plugged in to it (headphones or power cord), and then to connect the headphone jack slowly also.
this has been working for me. it won't work if i plug the adapter in with the headphone jack already connected, but only if i plug in only the adapter, then plug the headphones into it second, it works just fine.
i've found that i can have the power cord plugged into the adapter when i plug it into my phone, just not the headphone jack.
this works for me using this adapter:
i can finally stream music in my car again!