How long have you waited for the system to possibly de-freeze? You can let the computer be frozen for 15 minutes and maybe it will reset the driver that fails or do something else. If there is still no reaction from the system after 15 minutes, you can reset it. After your pc has started up, take a look in the Event Log (Start -> Run -> eventvwr.msc) to see if you see any Errors / Warnings that could be related to your problem. Possibly you can find something in the System log.
Also, if after the reset a message shows up that the system has been recovered from an error, you should submit the data and see if the Microsoft website says something more about the cause.