Same here.
It's not all the time, but it seems like the phone has some sort of accidental touch detection, but only in certain situations and it's not implemented very well. It's been a "feature" of all the ICS leaks that I tried as well.
hmm reading this , here is a hunch , could it have something to do with the wake screen thingy , like you know how it dims before it woudl shut the screen down , cuz everytime I unlock my phone and click anything right away on my phone this doesnt happen .. Ijust tested it liek 20 times in a row but coud be afluke