Getting the same problem here on my device, suddenly. I updated to the new Kit Kat update (I'm on Sprint) but didn't seem to make a difference. How annoying this suddenly happened and my phone was not dropped or damaged or anything. My other friend with a G2 had the issue and it went away on its own over time somehow. i'm noticing the bar where I have trouble is aligned exactly with the power button on the back, so I wonder if that has something to do with it, in the hardware.
Device history: LS980 (Sprint LGG2) > Samsung Galaxy Nexus > Samsung Galaxy S2 Epic 4G Touch > HTC Evo 4G > HTC Hero > Motorola Q9C (Win Phone 5.1) > Motorola Q (Win Phone 5.0) > Sony Palm Pilot