Rainbow screen during boot/random beach ball hiccups

[Phill-art]

I have a MacBook Pro (17-inch, Mid 2010) Snow Leopard 10.6.8 with 4 GB of ram. I have 220.77 GB of space left on my HD.

When I booted my computer up, after the grey screen with the apple logo, a rainbow screen that looked like this came up.

The rainbow screen eventually went away and turned into a blue screen, but wasn't booting even after 5 minutes or so, so I did a hard shutdown. I tried booting again, and waited longer, still no luck. Then I booted in safe mode and inserted a Snow Leopard install disk to run disk repair during the next boot. After that, it took awhile to boot up, but did so successfully. Booted fine after that for a couple days, then the rainbow screen came up again. I did a hard shut down and then it booted up fine.

As far as the beach ball hiccups, it happens in all programs randomly, for about 5 to 10 seconds.
I've tried:

Looking at the Activity Monitor, nothing seems to be using up a huge amount of CPU (same programs I used worked fine before my mac suddenly slowed down).
Uninstalling chrome (COMPLETELY) and used firefox, made no difference, so I uninstalled firefox (COMPLETELY) and installed chrome again.
I disabled the flash that comes with Chrome as well. (which can cause problems apparently with the flash already on the system)
Running an extended hardware check (no problems found)
Resetting the NVRAM and PRAM
Resetting the SMC
Running Disk Repair
Repairing Disk Permissions
Having no login items
Cleaning up my desktop
I ran OnyX (cleans up all caches)
I have the latest system updates
I have the latest version of Flash

The only thing that happened before I noticed my mac slowing down was: I woke my computer when it was running very low on battery power, it woke instantly. Usually the screen takes a second to come back from being asleep on low battery power, so I thought it was unusual. Did I interrupt it from going into a deeper sleep cycle and glitch something out?

 

[T5BRICK]

Looks like a GPU related problem to me. You've tried quite a few troubleshooting steps, but have you tried re-seating the RAM? I doubt that's the problem, but it's worth a shot.

The 15" models from this generation had a GPU related issue that popped up in 10.6-10.8.

 

[Phill-art]

Damn, I have to open my mac? Guess I'll think about taking it to an Apple store, I have zero confidence in fixing hardware issues. So does reseating the ram have to do with the rainbow screen AND the freezes?

So if it's a hardware issue, why doesn't the hardware check catch it?

 

[T5BRICK]

Damn, I have to open my mac? Guess I'll think about taking it to an Apple store, I have zero confidence in fixing hardware issues. So does reseating the ram have to do with the rainbow screen AND the freezes?

It seems to be GPU related and if I recall correctly, the model you have actually contains 2 GPUs. One of those uses a portion of the system memory for VRAM and re-seating the memory is fairly easy.

So if it's a hardware issue, why doesn't the hardware check catch it?

AHT is a good test but it doesn't catch everything. You could set it to loop and run it overnight to really stress the computer. Maybe an error would pop up.

 

[Phill-art]

I'm afraid I'll get something dirty or press to hard on a part or something. Call it OCD.

I'm wondering if this GPU issue has anything to with my computer running too hot for too long at times when connecting my mac to 50" plasma tv through a HDMI adapter... The movie would run on both the laptop screen and the TV screen.

Thanks for the help so far!

 

[romesk90]

AHT is a good test but it doesn't catch everything. You could set it to loop and run it overnight to really stress the computer. Maybe an error would pop up.

AHT does not get the macbook running too hot either so if a hardware issue is heat related it can miss it.

AHT does not catch everything like T5BRICK had said. For example, I recently needed to replace my screen (hardware issue) but AHT could never pick it up (my screen hinge was offset). There just is no test built for it.