Has anyone encountered this before?
The camera is relatively smooth on foot, but jerks up and down almost every frame while riding. It's nauseating and unbearable. I've tested running up and down the same hills, and also without any ENB at all, to confirm it is only on horseback.
It is particularly noticeable on the 'sharper' ENBs that don't have as much soft blur. I have the latest d3d9 file installed.

I have a 580 GTX.

Any ideas?