I know you probably tried this...but did you start out with the FS default flight?

I honestly am stupified why it started working for me..however..now that I have fixed that issue, I noticed that when I start the engines...I have no engine sound, AT ALL...I have uninstalled, my sound drivers (Realtek) then reinstalled, and even updated the driver after that didn't work. I also uninstalled the CS Pro pack, and the freighter, then reinstalled in the proper order and still no engine sounds. I have switch sounds and faint APU sounds, but that's it as far as the 757 goes. All other planes seem unaffected. Oh well, I'll keep working on it. Good luck with your radio issue.  :-/