It seems a matter of varying mileage.
Like Patrik, I have never had the slightest problem with the BVision / CGX v3 or v4 and have used it on OS3.1, 3.5 and 3.9 (CGX3 on OS3.1 / 3.5 and CGX4 on 3.5/3.9).
In fact, the only problems I ever had related to an early grex flash update that, unlike some reports here, didn't stop the card from working in 2D, but basically killed warp3d stone dead.