>>507893>Could it also be from insufficient light data? What about lamp sizes?
What kind of lamp are you using?
With a point- or spotlight there's not much you can do, with most other lights you can try to increase the size to make the shadows softer.
E.g. you can just scale an area light, or increase the "relative size" parameters of a sunlight, or increase the "theta angle" of a distant light.
This might help.
But if removing the bump mapping fixes the problem, try to decrease the bump amount as well.
Or, if you need such a strong bump effect, consider to use more subdivisions + displacement.
Or try a combination of all three of these.