On a really cold day in January, after I had the car for 3 months, the driver's side rear speaker began popping loudly. The popping slowed down and eventually stopped as the car warmed up. It continues to do this most mornings for about 30 seconds. The colder it is, the longer the popping lasts. I took it to the dealer, who ordered a new speaker. Now I have to make yet another trip back for them to install it.

Update from Aug 5, 2009: It turns out the speaker was not the problem. Naturally, the dealer could never recreate the problem. In 12/08, I saw a posting on the internet that there was now some sort of service bulletin about popping stereo noises and how the problem was with the in-dash unit, so I called the dealer and asked them to look up the bulletin. They found it, then said that they wouldn't order a new stereo unless they heard the problem themselves. I told them that it would have to be a freezing day in order for this to happen. They escalated my complaint to the manager, who asked me where the sound was coming from. As soon as I said it was the left rear speaker, he said they would order the part. (Apparently, as long as you correctly identify the magic problem spot, they fix it. Uggh!) Problem solved.