MacBook Pro (early 2006) users with ATI Radeon x1600 know these display anomalies desperately. These anomalies include horizontal lines on the screen, ugly distortions in images & videos and freeze ups / crashes (system crash) during normal usage.

I also have the same problem with my MacBook Pro. In my experience, this issue is related with firmware and hardware. I’ll explain them but first of all, if you have this problem with your MBP, don’t waste your time to reinstall Mac OS X, because the problem isn’t about OS X (Leopard, Snow Leopard…etc).

Firmware:
Problems with horizontal lines and system crashes began in mid 2008 after some firmware update. Some MBP users say; “I never had any problems with Tiger, then installed Leopard and all of a sudden my computer’s crashing all the time.” Yeah, this is true, but it is not about Leopard or Tiger. After Apple updated the firmware in 2008, then problem with display anomalies began. So don’t try to reinstall OS X. You can’t change your firmware, also you can’t revert to the old firmware too.

Hardware:
Overheating seems to be the important issue, once the temperature gets above ~ 65c usually system starts to exhibit graphics glitches, and then system crashes..etc. My MBP used to run at 78c (170f) at idle, wow look at the temperature at idle ! I even don’t want to talk about load temperature (around 92c). But before the firmware update (2008), there was no problem with temperature, temperature was still very high but wasn’t getting graphical errors or crashes.

Possible Fixes

smcFanControl
You can try smcFanControl. This little application lets you monitor the temperature and fan-speed of your intel mac. You can also set the minimum fan-speed for every fan manually and cool down your intel mac. I have been using smcFanControl for years, which does help significantly, but does not help when the computer is running 78c at idle (even with fans at 6005 rpm).

Reapply the Thermal Paste
I haven’t changed the thermal paste yet but some users did it.
Torley.com: “last saturday i’ve tried to change thermal paste on the GPU and CPU. I’ve seen that Apple Thermal paste was crunchy and solid. I’ve change for new artic silver 5 paste. But there is still horizontal line as soon as the temperature of GPU is over 60°C. But no more freeze…”

Clean your MacBook Pro
You can tightly and carefully vacuum the rear vent (where the screen meets the main body of the MacBook) with vacuum cleaner. This cleaning procedure maybe decrease some degrees of temperatures.

Install Windows / Linux
Somer users switched to Linux or Windows full-time and they say that the problem seems to have gone away. But I have to say that I haven’t had the same experience with them. When I boot into Windows XP, the splash screen displays anomalies. I even couldn’t install any Linux distributions (Ubuntu, Mint..etc) because of system crashes.

Main Solution

In conclusion, my MBP got worse and worse over time and I was only able to boot in safe mode. So my last chance was to remove ATI drivers from the system. When I removed the drivers, anomalies and crashes were all gone. You should know that; after removing these drivers, you won’t be able to play games and won’t be able to use 3d applications (Blender…), movies (VLC), pictures (Preview)… (*you can use other programs for movies & pictures like Chroma, QuickTime, Picasa…) I know this isn’t a concrete solution to problem but at least you will be able to use your computer without any display anomalies or system crashes.

Boot your MacBook in safe mode (immediately after you hear the startup tone, hold the Shift key), and delete the files above and reboot.

Here is the list of files to delete:

/System/Library/Extensions/ATIRadeonX1000.kext
/System/Library/Extensions/ATIRadeonX1000GA.plugin
/System/Library/Extensions/ATIRadeonX1000GLDriver.bundle
/System/Library/Extensions/ATIRadeonX1000VADriver.bundle
/System/Library/Extensions/ATIRadeonX2000.kext
/System/Library/Extensions/ATIRadeonX2000GA.plugin
/System/Library/Extensions/ATIRadeonX2000GLDriver.bundle
/System/Library/Extensions/ATIRadeonX2000VADriver.bundle

If you want to put the drivers back, just download the combo update from the Apple’s site and reinstall it. You don’t need to reinstall OS X, just download the combo update and install. Combo update will put the drivers back.