Hello duffscudder,
And welcome to Apple Discussions!
I don't have very many suggestions for you, but I thought I would at least tell you what I do know or think you should at least try at this point. The situation is more unique in that the problem only occurs with an older iPod model, which in and of itself, could be the very issue here.
So the fact that your Windows 7 machine recognizes all other Apple Devices except for the 4G iPod says that the issue likely lies with the older iPod itself. There could be a possibly that its connector port is damaged or worn out from normal wear and tear so much that the computer can no longer properly communicate with the device. Have you tried plugging it into a different machine if at all possible to see if the issue persists there? If you can, try it on both a 32-bit and 64-bit machine to see if there if the problem occurs on both.
Are you using the same cable on the 4G iPod as you are on your other Apple devices? Does this happen with whatever USB port you plug it into?
Again, I know all the other devices are recognized just fine, but it still might help to try and troubleshoot the iPod drivers as described in this article.
http://support.apple.com/kb/ts1538
B-rock
