I'm surprised that I have not come across this specific problem in these forums or in support. Ati 5470 driver has problems in 64 bit windows 7. There was problems with the original driver that caused the display to become unstable when coming out of sleep and was only alleviated after a forced reboot. The driver update offered by Dell fixed this problem only to cause a new one. Now, when in multiple monitor mode, the displays keep switching back and forth between the notebook display and the 2nd monitor which is a flat screen TV. Switching back to the older diver fixes this but has the previous problem again. The new Bios update (A09)  has helped slow down the process of the 2 problems mentioned, so that the switching occurs less frequently with the updated driver, and the driver instability is less violent with the old driver. Downloading the driver posted on the ATi website does not solve the problem.

I have even reinstalled the whole OS with no success.