Yup, I'd say so, too. Acceleration cache wants disabling.
I haven't seen this problem for a good while now, it's usually very apparent in 2D clouds when any acceleration is enabled, I have also had it in 3D clouds, too, though.
Usually, it's when I'm looking directly north(which I nearly always do) and there is cloud coverage, or cloud shadows on the terrain with a visible cut-off(cloud shadows seem to be more prone to this anomaly for me now, than actual clouds).