ok, so this thread, old as it is, was beneficial to me...here's my story...
i have three touchpads, but one i gave to my daughter for her birthday last year, and i have two that i use. my daughter's is in a nice case i bought with very hard sides and the ability to stand up at three varying angles. the two i use are in official HP touchpad cases.
a couple times i have had the two laying on top of each other and never thought anything of it. a couple weeks back i picked up the one that was on the bottom of the stack and opened it and turned it on. there was the ring...a brownish reddish hue to it, right there as obvious as can be on the homepage of google! i couldn't believe it, what was happening.
i turned off the tablet, plugged it back in and left it to sit. a couple days later i went back and it was gone...fast forward to a couple weeks later and there it was again only this time it didn't go away. not even a little. i searched around on the web, but i wasn't really onto what was going on. so my buddy swings by one night and goes "don't these have that magnet charging thing built in?" and then it hit me that might be it, and it was right in the middle of the screen in an oval shape just what i could picture the magnet would look like.
anyway, i found this post and read it and went out back and grabbed a suction cup i had...stuck it on...and pulled on it. then i separated it from the screen and removed it...sure enough, the ring was gone. very strange.
i think POSSIBLY the one touchpad sitting on top of the other doubled up the magnet strength or had some kind of opposite pole effect...i am not sure, but that ring was there for almost two weeks. ten seconds with the suction cup and it was gone.
the moral of this for me is, no matter how strange it sounded about using suction to fix this, capacitive screen and all, and as much as it seems to go against common sense...it worked. i had almost given up on that touchpad ever coming back to normal...thanks guys!