Hello, I successfully started up my aircraft, and the radios wouldn't work.  The COM master switches were on, I could see ter frequencies they were dialed to, but I could not change the frequencies or contact atc.

Reading another post in the forum, I assigned a key combination (ctrl-shift-a) to the avionics master switch.  When I did this my radios started working again.  However, about 5 minutes later just before I took the runway for take-off, they stopped working again.  Same as before, the master switches are on, I can see the frequencies, but I can't contact ATC or change the frequencies.  

Before starting the aircraft, I loaded the default C172 and turned off engines, avionics, and battery, then loaded the C-130.

Yesterday, I did a flight where I used ctrl-e to start the engines and didn't have the radio problem.

Thanks for any help.