I've been able to reproduce this problem so many times on my own system in different accounts it's not funny.
Here are the steps to reproduce:
1. Open iTunes and select your AX-connected speakers. (Make sure this preference sticks)
2. Leave iTunes open.
3. Let the computer go to sleep. (I have done this via Energy Saver on a schedule)
4. Awaken the computer.
"Multiple Speakers" is now selected in the pop-up menu. Both the speakers (AX) and your computer's output are selected. When you try to playback any music you will get the following:
"An error occurred while connecting to the remote speaker '(name).' An unknown error occurred (-3256)."
Then the music will playback from the computer. Unchecking "Computer" from remote speakers and attempting to playback by selecting the AX speakers will result in no sound. Switching back to Computer and again to the AX speakers will have the status window show "Connecting to remote speakers" instead of "Connecting to (name)."
Now I sleep my Mac (PowerBook) every night on a set schedule and have it re-awaken the following morning. It's quite frustrating having to employ the workaround every time I want to first play music via iTunes.
I never had this kind of issue with 6.0.1 until this remote speaker "feature" showed up.