keyboard mouse freeze when plugging in ipod shuffle

Sometimes, but not always, when I have my ipod shuffle (4th gen) plugged into my early 2008 Mac Pro, the keyboard and mouse stop functioning. The computer continues to work just fine, but I cannot interact with it, and no amount of un/replugging in the devices makes any difference, and I end up having to forcibly restart the machine, which I really hate to do.

Has anybody else seen this behavior? Anybody have any idea how to fix or why it may be happening? I am using the connector cable that came with the ipod, and plugging it directly into a port on the Mac.

Thanks