Q: Red and green square dots?

Well...it's been 6 days since Apple "fixed" the problem by wiping the drive and now the pink squares are back. They're a bit more subtle than before, but i bet it will get worse.

Picked up my iMac again. They replaced the logic board and the graphics card again. They said the first graphic card that was place got fried. So all is good so far no dots. I'll report back in a week and let you know if I see and dots.

This time I didn't get charged by Apple for the repair only out for the 1 graphics card so I made out on the deal. I still think it should be a recall because so many people are having the same issues.

Well, we have 2 iMacs in our office.  One is on Mavericks, the other Mountain Lion and both show it.  The one with Moutain Lion had the video card replaced while still under AppleCare and that worked for a month or two.  Both had the symptoms come back.  We have about given up as the machines are mission critical.

Oddly I did the simple suggestion on here of never letting the monitor go to sleep.  Since then neither has had any issues whatsoever and it has been more than a week. 

What a mess.

When you say never sleep do you mean never turn off screen? As in, just using screen saver?

I changed it in the Energy setting.  You will get a warning that you could shorten the life of your monitor.  We are running a screen saver.  But for me the energy setting was key...

Yep, turning energy saver off for the screen also worked for me.  It's only been a few days, but that's longer than I have been able to go.  Question is, now that the issue is identified, how can we report this to Apple to get a fix in a future update?

Since my energy saver resets ("never" for screen - using the energy saver, then activating a screen saver program), I've not experienced any crashes, freezes, nor restarts.... and no "pixelations"!

Had occasion to converse with AppleCare techs yesterday re a defective iPhone 4S, and we discussed this issue at length during that hour-long conversation. Despite his experience as an iMac tech (as well), he'd never heard of this. so I asked if he might review these blogs and bring the extent of this issue to Apple's attention for a "global" resolution.

Fingers crossed...

Isn't it just beautiful?! Had it at the local Apple Service Provider this week with no luck, they couldn't even reproduce the dots. Could it be something that is connected to the iMac? I'll try the energy setting and set it to never sleep and just use the screen saver instead.

I changed my `Energy Savings` settings to `Never` for both `Computer Sleep` and `Display Sleep` then rebooted. The pixelation, freezes and crashes disappeared for maybe a day but, I am experiencing the problem again. So I'm going to be frank and say, “Nothing fixes this problem not even the Energy Savings work around!”.

I remember one more strange thing about my iMac which has not been seen in this post. I have burned through 2 monitors connected via the `ThunderBolt|DisplayPort` . The first one was old and I just thought it was just it’s natural death. When the next one (also old) died I thought maybe I’ve just had the resolution too high and burned it out. I got a more powerful monitor and this issue started happening.

The cabling was `ThunderBolt|DisplayPort` -> `DisplayPort to VGA adapter` -> `VGA cable`. It took a few months for the “old” monitors to die. FYI: My new display is connected right to `DisplayPort`.

Well the energy settings change has worked for me. The daily occurance of flashing colored blocks has now not appeared for a week since setting the screen to never sleep and only use screen saver. I suspect that it is hardware issue and this fix may only work until a certain level of degradation,

some crazy (but welcoming) news on my machine: the glitches, pixels, random crashes, etc. have FULLY CEASED without doing any voodoo tricks or prying the case open. Nothing. Just one day it's gone and hasn't returned. Like a bad rash or tendonitis that simply vanishes.

What's the scientific explanation for this? Hardware pathways connecting purely with luck at the atomic level?

I'm not sure if I'm having the same success, but here's the latest on my 2010 27" iMac.

Apple first told me that they would replace the graphics card. After more extensive testing, they determined that it was more likely the logic board. I was comfortable taking the risk on a $250 graphics card, especially because they promised to take care of me if that wasn't the real problem. When they called back to say that they wanted to replace the logic board for $600 - and I still might need to replace the graphics card - I decided to decline the repair.

I bought a new iMac, because my wife and I were tired of dealing with the issues with the 2010 machine.

For the past week, I've had both the new and old iMacs running. The 2010 iMac seems to be working fine now. No graphic distortion or shut downs.

We are going to exclusively use the old iMac for the next couple days. If we don't have any problems, I'm taking the new iMac back to Apple for a refund.

Have we had any software updates that would have resolved this issue in the past 2-3 weeks?

ummm, I haven't seen a pixel out of place for a couple weeks now. So bizarre, but stoked. If Apple did something behind the scenes in the Mavericks platform, then call me Larry the Cable Guy. Because I was convinced we were dealing with hardware issues. if it was driver/software spangola; you're speakin' greek to me, get 'er done!

I tried most of the suggestions in this thread. A complete os reinstall seemed to help for about a month but now the problems are back and as bad as earlier.....panics, pink squares etc.

Disable energy saver did not help so I thought of another test. I dowloaded a GPU stress test that i've left running for the past 3 days. This keeps the GPU on a high steady temp and all the panics etc are gone. This is not a solution but it looks like the problem is hardware related in my case.

Maybe baking the graphics could help :)

Perhaps I've just been inordinately fortunate, but it's been weeks since I changed the energy saving settings and I have yet to experience a repetition of the shimmering pixels....

Fingers crossed that my issue's been resolved....

mid-2010 iMac i5 27"