[Elecraft] IO Problem

[N5MF]

I have an unusual problem may some one can help with

My K2/100 has stopped talking to my computer.  

I have tried 2 computers thinking it was the serial port but no

I redid the cable and still nothing

Finally I changed the amp lid with the QRP lid and it all works fine.

I have a KAT 100 tuner as well and the rig does talk to the tuner and everything on the amp and tuner works.  ie power, tune, antenna switching.  The rig just doesnt talk to the computer.  Like I said it works with the IO on the qrp lid and the settings on the computers are correct and the IO is on on both the KIO and the K100

Any thoughts

Mark
N5MF