This happens in the "Enemy Within" campaign. I am using 2.5 beta, and the latest update, which I installed today. This is on Win10. When attempting to use the radio (the one used to contact ATC, etc.) I am unable to use any frequency but 132.000 When I try to use 133.000 for example, I'm not able to contact ATC. After setting the freq to 133.000, I use "" or left alt+keypad num to get to radio menu. There, I see an entry for Kobuleti grayed-out, and only get the F2 option for default airport. When I select that and contact them, the radio frequency changes to 132.000 (on the frequency selectors) and of course, I get no answer from them. I've tried this with 134-137, and the same results. I have not tried it with missions or instant action yet.
I also get no ILS or TACAN signals from Kobuleti (111.5 & 67X respectively) when coming home. Hope you can fix these soon. It's hard to fly a campaign without radio contact.
Reverting to the previous version.