I have the same exact hardware problem, though I never turned the TouchPad on to see the effects
Update: I spoke with HP Customer Service and they agreed it was defective but were unable to offer me a replacement because they didn't have any in stock. I was told to contact Tech Support and given a live chat link (remove the '~' since I can't post links yet):
Here I was given two options:
If your device is in warranty then you can choose the Repair and Return with Box option at no charge. We’ll send you an empty box with a prepaid label in which to return your tablet to our repair facility.
The process takes 7 to 10 business days from the date you ship your device. After repairs are made, your device is returned to you using 2-day air.
In addition, we have a premium option that is faster. We can send you the empty box overnight. Then the turnaround from the date you ship your device is 5 to 7 days. There is a fee of $29 for this premium repair option.
I asked for a new unit to replace my defective one, eventually got escalated, and was called back the next day.
The rep assured me that any replacement unit would be in 'like new or better condition' and offered "Advance Exchange" - where I receive a shipment containing both a replacement TouchPad and a return box for the defective device. The "Advanced Exchange" service has some associated charges, but those were "negotiable" and the rep waived them. I was asked to provide credit card information for a ~$300 hold until the defective device returns, I objected, and it was kindly reduced to a $1 hold (though surely they reserve the right to charge the full amount if necessary).
Hope everything turns out well.