[Elecraft] KRC2 does not communicate with CPU

[Gordon LaPoint]

I have 2 KRC2's, one is working correctly with my K3. The second one 
used to work, but now just blinks the LED slowly, about 1 sec. rate, 
when powered up.  If I switch the OP/DL switch to DL the LED turns off.  
I have no comms over the serial port with my computer.  I'm using the 
same setup as the one that works.

I tried to D/L new firmware, but it never finishes and the symptoms 
never change.   Is the PIC16F877 fried, or the serial interface chip 
(MAX1406)?

Any suggestions on what to try?

Thanks,

Gordon - N1MGO