[Elecraft] No output on CW with K3

[K4GM- George]

My K3 using 4.22  will put out full power in TUNE position. The ATU 
works fine and delivers 1:1 swr or close. However, if I switch to CW I 
get zero power out. I switched to 5 watts out and still no power out on 
cw. I hear the sidetone as I key and the radio appears to go into 
transmit mode because the RX is muted.  RX is fine. These conditions are 
the same on all bands 160-10.  Switching to RTTY FSK D or PSK D I do get 
full power out.  AFSK A also works fine.   Suggestions??  Firmware issue 
or hardware problem?  Naturally this happened in the middle of a contest!

George Marzloff  K4GM