You don't need to "death grip" it to experience the issue. Hold it in your left hand and you can EASILY and ACCIDENTALLY replicate the issue. I had noticed it even before it was brought to the "public eye" or even these forums. I wasn't sure what was causing it until I realized that holding it in my left hand my palm touched the black line. You don't need to do some kind of death squeeze on the device to cause the problem.
Originally Posted by BuddhistGirafe
I'd say hopefully you won't have the problem in Canada b/c of a different network, but people in other countries have experienced the problem, so it's not just an AT&T issue.