My first thought is external power problems. If the venue is not earthed correctly or your cables have poor earth bond you will get issues with digital equipment. For the sake of a few dollars you can buy a simple plug tester, basically an ac plug with three LED's that tell you if the socket is safe to use. It doesn't test for earth bond though. (for this you will have to make a visual check or have an approved PAT engineer do it for you.

If your Audya had a problem at the same venue or using the same extension cables/ac cables then I would look there before spending your own time and money having the keyboards checked out. With a lack of test equipment if your on a gig, then one simple method once everything is powered up (its easy on a Ketron as they are metal) is to gently stroke the metal surface with your finger tips, if you feel a light 'buzzing' sensation when the equipment is on, then you have an earthing problem and you should not play until it is fixed. If its the venue at fault flatly refuse to perform..the responsibility is there's alone and you should still demand your fee if they refuse to get it looked at.

It never ceases to amaze me just how many high profile venues have dodgy wiring. A bad earth is not just an annoyance as it messes with your equipment it is a real hazzard to your health.

I am convinced that crashes and glitches with metal digital keyboards occur not because of any particular operation, but because you are touching the metal panel temprarily earthing the keyboard using your body!

something like this is good for quick checking of venue outlets and should be part of anyones gig bag:
http://cpc.farnell.com/pro-elec/t203/mai...e-bb45-00001001