Upper half of the screen is scrambled with nvidia driver

[Hendrik Lönngren]

The driver nvidia-331 produces a scrambled screen on MacBook Air 3,2 (NVIDIA GeForce 320M) running a Trusty live system. It looks like the attached image.

I have figured out in what way the display is scrambled. In a numerical representation of the pixels that increments row-by-row (but where the rows are 16*92=1472 pixels wide, although the screen is only 1440 pixels wide), bits 4..10 become bits 9..15 and bits 11..15 become bits 4..8. More precisely, this is the code I used to reproduce the scrambling:

---

int main()
{
  cimg_library::CImg<char> img("desktop.png");
  cimg_library::CImg<char> img2(1440,900,1,3);
  for(int X=0; X<1440; X++)
    for(int Y=0; Y<900; Y++)
    {
      int i = 896 + 92*Y + X/16;

      if(i/4096 < 9) i = i/32%128 + i%32*128 + i/4096*4096;

      int x = X%16 + (i-896)%92*16;
      int y = (i-896)/92;

      for(int c=0; c<3; c++)
        img2(X,Y,0,c) = i>=896 ? img(x,y,0,c) : 0;
    }
  img2.save("scrambled.png");

  return 0;
}

---

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: nvidia-331 331.38-0ubuntu7
ProcVersionSignature: Ubuntu 3.13.0-32.57-generic 3.13.11.4
Uname: Linux 3.13.0-32-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.2
Architecture: amd64
CasperVersion: 1.340
CurrentDesktop: Unity
Date: Wed Sep 10 11:23:43 2014
LiveMediaBuild: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: nvidia-graphics-drivers-331
UpgradeStatus: No upgrade log present (probably fresh install)