Sorry for the sketchy description. Both monitors go black and computer power light is blinking. The only option is to shut the computer off and power it back up.

 

At this point, this may be a coincidence of coincidences. Prior to the update, I had just moved to 20 m from 40 m where I had raised the transmitter from 5 w (normal power) to 20 w. Prior to this I had never transmitted on 20 m at above 5 w. Even tho my antenna is driven by an antenna tuner and SWR at transmitter is under 1.2 : 1, it appears, on 20 m, I have a grounding (maybe ground resonance) problem. Reducing power to my normal 5 w fixes the problem so the update does NOT appear to be the problem. Now looking at how to improve grounding with very dry sandy soil.

Sorry for false alarm. 

Chas (W8IAI)