headphones or speakers/cassette?
I have the same problem whenever I use anything OTHER than headphones. Standard headphones DO work with the adapterfor me. But external speakers and car cassette adapter does not. My adapter is brand new. Didn't work before OR after the Windows Live 6 upgrade. Grrr, as the majority of hte time I want to play music in the car.
UPDATE: THE PROBLEM IS THE ADAPTER
I had bought an adapter that looks like the one pictured in the above post. I took it back to Radioshack and explained the problem and asked if they had a DIFFERENT kind of 3.5>2.5 adapter. They took me back to the stereo section, where they had one that is straight without the cable. THAT ONE WORKS GREAT! And it was about half the price. They said they sell the other one up front with the phones "because the iPhone's jack is recessed and won't work with [the straight one]". (Hmm...not because it costs twice as much?)
The new one is RadioAhack part number 274-373 1/8" to 3/32" adapter. Hope that helps!