Plot looking bad

[Huub]

Hi,

Using Fedora 21 and Octave 3.8.2 on a pc with nVidia video NV34 chipset, I want to do a simple plot:
x = linspace(0, pi);
plot(sin(2*x));
Instead of a sine plot, I get the result in the attachment. I got a similar result using Fedora 20 with same Octave version. Does this mean that Octave (or plot) doesn't support this video chipset anymore ?

Thanks.

octave-plot.jpg
Description: JPEG image