could be your power strip
could be your extension cord
could be the outlet on wall
could be sudden power failure, like quick lightning
could be lots of things

for it to happen to 2 keyboards leads me to believe its not the keyboards

the only way to PROVE or find out why is

put a UPS on the AUDYA !!!

Diki, would be the 1st to recommend a UPS as i believe he uses one all the time...