I'm using maxed settings + ugridstoload at 9. (Before the ugrids, was the same issue).
Also i'm using the Realistic Lighting mod.
The shadow is appearing on the ground, as a fishing net, or some kind of zebra, and if i move the mouse in some direction the shadow disappears and re-appears, while e move the mouse in some directions.
I've never played Skyrim for a while, and this could be a patch issue ? Also i have AF x16 from the driver enabled for Skyrim.