They say that wise men learn from the misfortune of others, so here's an opportunity to get wiser on my dime.
I synced Sandy's iPod Touch 32G today since she had purchased a new album from the iTunes store. The iTunes software pushed software version 4.1 down to the iPod as part of the sync.
Tonight, I connected the iPod to the 730N entertainment/navigation system in our truck (see signature) using the iPod direct connection cable. After playing for about 1 minute, the system would shut down with the 730N displaying a Communication Error message. Restarting the system required unplugging and then reconnecting the iPod, then reselecting the iPod as the desired input device from the 730N's screen. After all this, it would play for 1 minute and again shut down with the Communication Error message.
On the Apple iPod support forums, other users are reporting similar problems with Hyundai, Toyota, BMW and other entertainment systems. Apparently the problem began with Apple's software release 4.0 for the iPod and has yet to be resolved.
Moral of the story - if your iPod is now communicating directly with your OEM or aftermarket vehicle entertainment system in a satisfactory manner, do NOT upgrade its software. I have no idea if Apple is working on a fix, but until then, I'm back to playing the iPod through the 730N's auxiliary input jack.
Rusty