[Elecraft] K3 Serial port problems?

[Ross Primrose N4RP]

I've recently lost the ability to communicate with my K3. I've tried it 
on two different computers, both with real serial ports, and used two 
different cables. I've got PTT-KEY set to dtr-off and dtr PTT still 
works, but I am unable to communicate with the radio with the K3 utility 
or any rig control software. I've tested both of the cables by plugging 
in my RS-232<->CAT adapter for my FT-817 to the K3 end of the serial 
cable, and I have no problem communicating with the FT-817.

Ideas on what to check next?

Thanks, and 73, Ross N4RP

-- 
FCC Section 97.313(a) “At all times, an amateur station must use the minimum transmitter power necessary to carry out the desired communications.”