MacBook Pro running external monitor shows green sparkles

Question

I'm trying to use an external display with my MacBook Pro laptop. The laptop detects the display and the display is running at its native resolution of 1680 by 1050.

However, there are constant green pixels randomly flashing on and off evenly across the entire display area.

The display is connected via a mini DVI to HDMI adaptor.

I tried power cycling everything.

I also verified that this display works fine with a different MacBook Pro -- a much older one with the old HDMI out port.

1. Is anyone else seeing this problem?

2. Is there any way to fix it?

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The computer

  Model Name:   MacBook Pro
  Model Identifier: MacBookPro5,4
  Processor Name:   Intel Core 2 Duo
  Processor Speed:  2.53 GHz
  Number Of Processors: 1
  Total Number Of Cores:    2
  L2 Cache: 3 MB
  Memory:   4 GB
  Bus Speed:    1.07 GHz
  Boot ROM Version: MBP53.00AC.B03
  SMC Version (system): 1.49f2

NVIDIA GeForce 9400M:

  Chipset Model:    NVIDIA GeForce 9400M
  Type: GPU
  Bus:  PCI
  VRAM (Total): 256 MB
  Vendor:   NVIDIA (0x10de)
  Device ID:    0x0863
  Revision ID:  0x00b1
  ROM Revision: 3448
  Displays:
Color LCD:
  Resolution:   1440 x 900
  Pixel Depth:  32-Bit Color (ARGB8888)
  Mirror:   Off
  Online:   Yes
  Built-In: Yes
LA2205:
  Resolution:   1680 x 1050 @ 60 Hz
  Pixel Depth:  32-Bit Color (ARGB8888)
  Display Serial Number:    3CQ0132VF9  
  Main Display: Yes
  Mirror:   Off
  Online:   Yes
  Rotation: Supported

The monitor

HP Compaq LA2205wg

Answer 1

It could simply be a faulty adapter, or a problem with the input port itself (a damaged pin or the like). Try another adapter, or the same adapter on a different machine.

There could be a problem with the internal graphics card as well, although that's relatively unlikely if the internal display is working fine. Still, to rule it out, you'd need to try an entirely different monitor on this machine.