Toyota Camry + TomTom GPS = No Go!

jasongroves, Oct 25, 7:49am
I am asking this in behalf so am only going on info given to me:)
2000 Camry import with factory Japanese inbuilt all in one GPS unit.
Owner bought a Tom Tom GPS unit for it a while back.
The issue is that it wont work in his car once the car is started.
Works find when the key is off but as soon as key is turned the screen goes blue. Doesn't matter whether the GPS is plugged into the lighter socket or not.
Unit is not faulty, as it works in every other car he has tried it in.
Very strange and quite frustrating for him.
Anyone experienced anything similar!
Could it be interference of some sort from the factory unit!
Thats about the only thing I can think of, otherwise I'm pretty much at a loss!
Would be very grateful for any advice as would really like to help this guy out if possible (he is a retired bloke who is a regular at the pub I work at).
Cheers all:)