update 3/20/09
Weird: I took it into the dealership and they were Unable To Reproduce. Actually the speaker problems were gone by the time I got it there...
They hadn't checked the phone/radio interaction originally because (of course) I hadn't left them my phone. And they did road-test it for the radio - with an Aston Audio Specialist - because that was my main complaint at the 10,000 mile mark. Again, they were very skeptical, as they've been for a year and a half, that anything could be done for the AM radio. But when I insisted, they spent 3 days and got it working perfectly. I paid the $2,400 and drove it home. (What's that nonsense I read on here about $800 tuneups? Mine was $2,950 at 6,000 miles - including 1 new tire - and $2,400 this time including new rear brakes. The freaking pollen filter alone is $330 and the air filter's $415. Labor was $1,370...)
So this time, after the problems described in my earlier post were deemed irreproducible, they "cleared the codes" and I drove it home again.
And the radio and CD player both began auto-muting again. Every time the car was started, they played for 3-5 seconds, then MUTE.
Rather than take it back, I kept driving it, and this problem too seems to have abated.
The whole deal reminded me of when I used to collect complicated watches. Your basic $10 Seiko will run forever, but a $75,000 Patek Philippe perpetual calendar chrono stops running once every 3 years and costs $2,200 and 18 months in Geneva to fix.
I've got to figure out a way to start admiring things with no moving parts.