Since clients are talking to this particular CM9 I assume your using a sector or an omni? Are you using Coax surge protector that is properly grounded? Atheros cards are using a rf selector switch which is fairly sensitive and easily get damaged which results in about 20dB signal loss which in
I had something vaguely similar happen... The radio would stop passing data. It turned out to be a client at around 10 miles that had set his cpe for G mode and was rapidly bouncing back and forth between G and B and up and down speedwise. Set him to B and no more misbehaving.