Wow, what's the title of the CD.

Is it Guns 'n' Roses "Search nav and destroy"?

Is the CD played in the CD player in the dash, while the nav is in the boot?

If so, the CD must be generating some very odd interference signal on the data bus / power lines that is getting into the nav. Very VERY strange.

Or is it "Deep Base Super Funky Thrash House" through a 10,000W amplifier that is causing such large voltage spikes it's upsetting the nav computer?