Range Rover Volume Problems

My 2002 Westminster Range Rover's volume isnt adjusting, also my navigation screen is blank white. I live in Montana and its the middle of winter, is this just the cold or something more?

probably something more or it would start working once it was up to temperature...

Any ideas of what it is?

I was told i need a Satellite Navigation Program Disc (LRL0568 Edition 3). I am wondering where i would be able to obtain this disc.

Well let me explain my situation. When i bought my car i had to fly down and pick it up in California. On the drive back to Montana I stayed in Reno NV. The next morning i walked outside and started my car. The navigation screen was black. This is my first Range Rover so i was unsure if this was normal or if my car had already broke within the first day of me buying it. I decided that i would let it just do its thing so i got on the road and started heading to montana. After an hour of driving i stopped for gas and when i started the car the navigation and the stereo volume worked again. I was extremely happy and thought it was just a spoof. When i arrived back in Montana i left the car outside in 5 degree weather for afew hours and then when i started it the same black, inoperative navigation screen appeared. I drove it around for half hour and when i came back home i parked it in the garage and after ten minutes i walked back out and started the car and it worked just fine. I decided that this car was just sensitive to the extreme cold and would just let it slide. Then one day i started the car and instead of a black navigation screen it was solid white. I recently took the car to my mechanic and he looked it over. He was unable to see any problems and he referred me to a service bulletin. This bulletin says..... "Inoperative NAV Display.......Vehicles can exhibit a condition where the NAV display will not function in cold ambient conditions. Cold Temperature can affect the internal communications during NAV system start up. The conditions may also cause a loss of radio functions during the warm up period. Both radio and NAV will return to normal operations once the vehicle has warmed." They say the resolution for the problem is to install new software configuration. They say that i need a Satellite Navigation Program Disc LRL0568 Edition 3, and then follow certain steps. The worry i have is that my problem went from a solid black screen to a solid white screen and since the solid white screen has appeared, once the car warms up, the volume control or the navigation doesnt return. I am hoping that this disc can fix the problem but i am wondering where to find the disc, and if the disc doesnt work, what is the next step?

Thank you for your help
Cameron