I have had an Evo 3D for almost 2 years now. No insurance, and started having this problem but top to bottom on the dead spot.
I fixed it by just altering the mouse pointer speed in the keyboard settings. I turned it up a bit, then slowed it down a bit. I set it back to how I like it and everything is working great. I was about to do a factory reset. I figured it was not a hardware issue, and really wish that it was not the default for the technicians to suggest that first thing.
I messed around with a lot of different settings, but this one fixed it. I have turned it off and on to verify it is still working fine.