I have a 2007 hummer h2 and the nav disc wont work...?

i have a 07 limited edition red hummer h2..i have had 2 new nav discs sent to me from gm that wont work in my h2 but work elsewhere..i have had gm send out 2 new radios also..nothing!!the dealership says its the disc..gm nav center says its the radio...does anyone have an idea what it might be?? thanxI have a 2007 hummer h2 and the nav disc wont work...?Well try a different disc. If it works, you've solved it. Sounds like the disc to me. Red Hummers always get lost.