I have seen this
"Many switch-mode PSUs misbehave if there isn't a functional ground. There's always a lot more conducted emissions and sometimes "interesting" symptoms - eg touchscreens can go totally haywire, not to mention RAM corruption and radio interference."
I was called to a conference room where a laptop was being used for an AV presentation. There was a loud, annoying hum in the audio that would worsen/get slightly better if you moved the AV and power supply cables. I noticed that the guy was using a 2-wire Dell power supply on his laptop. Having a moment of inspiration, I found one with a 3-prong, grounded plug and connected it. Instantly the hum went away.
Biting the hand that feeds IT
