Ramp Shader issue - Bug or driver problem?

So after saving for a long time I bought a new MacBook Pro which arrived this week. After getting all my files and settings transferred and sitting down to get comfortable with the new machine I noticed something in my models that use color ramps in their materials that doesn’t show up on my old 2007 MacBook Pro.

On the new system the edge of any gradient produced by the color ramp has a dark line associated with it and the “mix” blending mode seems to be completely different.

Steps:

  1. Open a new scene
  2. Delete the default cube
  3. Add UV Sphere
  4. Set Smooth shading on the new sphere
  5. Change the Viewport shading to textured
  6. Apply the default material to the sphere
  7. Check “Ramp” on the diffuse settings



Same settings / steps on older MacBook Pro…


Both systems are fully up to date on 10.6.7 running with the same version of Blender 2.57 (2.57.0 r36339m) user account and settings migrated from the old machine to the new.

This is really frustrating because several of my models make use of ramps on materials being mixed in the node editor for non-realistic realtime rendering in BGE where I planned to use them but if I can’t be sure that the shading will work the same across platforms then that means finding (and buying and learning) some other engine to use.

So am I screwed by a driver issue, some way ATi and nVidia do things differently, or is this something Blender isn’t doing right that it usually does on most hardware?

Thanks!