Clipping plane bug?
 

Not sure if that's the correct term for it, but I was getting this problem, especially in the commonlands while running to befallen for CR and such. Basically, depending on the angle your character was facing, the entire world disappears except for the sky background, but it's purely a visual bug. If I turned, it'd come in and out, and I'd eventually find an angle that would work for a bit, then it'd do it again, rinse/repeat. It wasn't happening in Befallen, and it hasn't happened in nro and such, just both commonlands zones.

Someone in guild said they had experienced the same thing, and thought there was a fix for it on the forums. I can't find it, cause I'm not sure if that's even the right term for what's happening.