Just a short tip that is probably not just true for the Intuos4 but also for other tablets and most likely for more different USB-devices. As I just encounter this on my Vista-PC I have this limited experience.
If you hibernate you computer, put it to sleep or however you may call it and you start it again with the saved session in memory, it can happen that your drawing tablet isn’t functioning properly. Rather than rebooting your computer you can solve this inconvenience with just unplugging the USB cable out of your Intuos4 and put it back in. Then it will function again without any problem.
Works every time for me.
Hope I saved you the time of rebooting with this. Have a good one!