I've just noticed something. Whenever I get a NAV radio failure on the default C172 (or any aircraft using the same radio panel), I can't change frequencies on the same COM radio. So, if NAV1 is out, COM1 can't be changed. And if NAV2 is out, COM2 freezes.Anyone else have this problem or know how to fix it?

Can confirm your findings, but unfortunately do not have a solution. When I first read your post, I wondered if the two were dependent on one another due to being many times inside the same physical box, but failing the comm's side of things still allows the NAV full operation. Hmmm...Kevin