MDX keys not working when next to iPhone

I have been experiencing a problem where the MDX keys will not work (won't unlock door using the button on the door) even if I am right next to the car when they are in the same pocket as my iPhone4s. It seems like there is direct interference. I also have BT enabled on my iPhone. As soon as I take the key out of proximity to iPhone, everything works fine

Has anyone else experienced similar issues? What phone?

I have used similar systems from Infiniti and others and never had a problem.

Any thoughts?

Any ideas on

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