replacement power adapter causes only touchpad to misbehave???

[paradoox]

I've just spent about an hour trying to cleaning the touchpad on my Dell E6510 which I use as the family room computer at Chez Wood. The touchpad was working poorly but the trackball (once I turned it back on) was working fine. I even went so far as to take the keyboard out to see how hard it would be to replace the touchpad (non-trivial). I was trying to figure out what I had spilled on the touchpad or something. Eventually it occurred to me that I was trying out a new "non-OEM" power adapter. (I bought it by mistake on Ebay. I should have realized the price was too good to be true and looked more carefully at the listing. But, since it was my mistake I wasn't going to send it back for the $10 I paid including postage, given the postage back would probably have been $5.) I switched back to the previous Dell adapter and the problem went away. I then tried it with just the battery and it also worked fine. This is weird because while the laptop technically requires a 90 watt adapter, it will run fine (but not charge well) on one of the 65 watt D-series adapters. I can only theorize that the non-OEM adapter isn't really putting out 19.5 volts and the touchpad is more sensitive to this than the rest of the computer or something.

I then tried the non-OEM adapter on one of my D630s and everything seems find there.

So, then I pulled out my trusty old (and I do mean old) voltmeter / multitester. I turns out the non-OEM adapter is putting out closer to 20 volts while the real Dell adapters are putting out closer to 19.5 volts.

So, the touchpad is sensitive to over-voltage?