Actually, I have always suspected it to be caused by the PlayStation2 's output signal and not the television. My suspicion is that it happens only with interlace mode.
It happens on my Dell 2407WFP-HC LCD and on my Pioneer plasma television set. I just don't have the cables to test my theory with progressive scan mode.
I have tried it on my 60gig ps3 at 720p and 1080i and i get the small sqare on the top of the left hand side at both resolutions.
So i dont think it happens in just interlace mode.
Its still pretty good on the ps3 more so with a g25 wheel.