My 2007 Acura MDX navigation does not work when XM radio is activated. I've replaced my drivers seats and upgraded the Nav/DVD disk a month ago (July 2015) and ever since then my XM radio doesn't work. I have purposely called XM and ask them to deactivate my account for a week and the NAV worked just fine throughout the week. However, now that XM is activated again it's not working. The dealer doesn't seem to know what wrong with with it.