ok this is getting REALLY annoying...

[Devon H]

ok so ALL the sudden today, for some reason i cant transmit on ANY freq. the keys are still assigned, i can transmit Voice-to-All but not a defined freq for tower and stuff...i even went as far as un-installing FSX and re-installing FSX and still same freakin thing...does anybody have any idea what the problem might be?

[BAW0343]

I'm guessing multilayer.  Sometimes the server is set up so that there is essentially only one Freq. so switching will do nothing.