You can install laminate flooring on a curved stair? There are new products out that's made to bend around a curved step. This is the stair nose I'm referring to..
Another way to remedy this problem is to eliminate the curve on the step. You would have to build the step out and make square corners. This involves adding additional material to the step. It doesn't matter if it looks pretty or not since you will cover it with the new flooring.
The only other alternative would be to install the stair nose in small pieces around the radius. This would result in a lot of seams where the pieces join and not look very good.