Today I started getting errors when I was connecting my Zune. After being connected for a minute or two, the Zune would show up with a yellow error icon in the Device Manager. The same thing happened when I first picked it up, but I was due for a reformat anyway and that solved the problem.
I was really confused when it started happening again this afternoon because it had been working just fine yesterday. It turns out that I had installed libusb today and apparently that doesn't play nicely with Zune. Since I uninstalled libusb, everything has been working fine.
Luckily that isn't software that I need very often, so I can just install/uninstall for the few occasions that I need it.