Most laptops shut off the network card when your machne goes to sleep. No network card=no network connectivity to the license server. On some machines, unplugging AC wall power also shuts off the network card. You'll need to dig around with the power management settings in Vista to see if you can disable this. It will depend on the hardware configuration specific to your laptop & manufacturer. If you have an internal IT resource, they should be able to track this down for you.
