Yep. I had exactly the same experience, and HP tech support walked me through it painlessly. This happens when you install the new driver without completely removing the previous driver. At least with WinXP; I don't speak Mac.
You need to remove all traces of the driver on your hard drive, and remove the Z3100 from your list of printers. If memory serves, you also have to edit a line in the registry to complete the removal. Then you do a clean install of the new driver, turn on the printer, plug in the USB cable and wait for Windows to recognize it and automatically install it. It's worth the trouble of clearing out an hour block in your schedule to have HP's tech support walk you through it.
With mine & Mac, it refuses altogether to load it, telling about a "server error", while the files to load are on my HD, without any server.
Your procedure might apply as well to Mac.