Q: OSX Lion + 2011 iMac 27'' + Video = Freeze

What Cantellolo is saying is that those of us experiencing the issue have updated everything, and are still experiencing issues.

I experience it every time I power down and reboot my Mac (or let it sleep and them wake).  I will have Kernel Protection Faults on boot up, and if that doesn't happen, random freezes from within any application (or even if no apps are open). 

I have confirmed today, though, that a reset of the PRAM means it will be stable for the entirety of the working session (as long as I don't have any power saving options turned on), so it appears that something in Lion is not working properly with the SMC in certain models of iMac.  Not saying that's the ONLY issue, but it does appear to be one (and is likely the culprit in my case).

I did not experience any similar issues prior to upgrading to Lion, but did experience my first freeze right after Lion completed installing.

Oh, and I waited to upgrade to Lion until after the second OS patch was released (so upgraded just last week).  My machine had been acting up when Lion was released (ironically, SMC issues, so Apple replaced the logic board), so wanted to wait until I was sure it was stable prior to upgrading the OS.  I didn't expect upgrading the OS to make it unstable again, though.

Well now, I appreciate your logical diagnosis. The way I see it, is that Apple have made changes and issued updates over the last four months. Also, you have to consider the many users of similar systems without this issue. So for me, at this stage, I would be looking hard at the third party apps on the computer. Did you try running in Safe Mode, to see if it makes any difference?

OK I know that a small percentage of users are affected, but if you happen to be one of those, then it's a one hundred percent of a problem for you!

I do have a "stock" account that has no extensions installed, and tried a clean install on an external drive.  The issue reoccurs even with nothing except Lion (and patches) installed (and, of course, apps that are installed with Lion like Safari and iTunes).

It looks like at this point, it's a bug related to specific combinations of hardware.  In my case, it makes it a little harder to diagnose, because my Logic Board was replaced by Apple (and prior to that, the Video Board), so it's possible those components are newer than what would be standard for when the machine was built.  It's either a serious bug, or I'm experiencing a hardware failure again and it's completely coincidental timing.

For now, I'm going to stick with the PRAM resets and see if another patch comes from Apple in the not-too-distant future.  If it doesn't get better, I may have to go back to Snow Leopard (there are a few Lion-only apps I'd like to keep running, though, so that's a last resort).

Based on the people experiencing issues in this thread, it does appear that Lion was a little undercooked when it was released.  One of the advantages of having so few Mac SKUs is supposed to be consistency of interaction with the hardware, right?

After seeing all these discussions, i am rethinking about buying new imac!!!

Wow am I glad I found this thread.  I was just given the green light to upgrade my Late 2006 iMac (which runs Lion flawlessly) and figured I'd look for issues with the new ones.  I was concerned to see this has been an issue for so long and for so many.  It looks like Apple just can't figure out what the problem is. I can't believe they haven't been trying.

Either way, it looks like I will not be buying a new iMac. 

I'm very sad to see this issue remains unresolved. This issue still lingers on my Imac despite trying all of the solutions people have posted, and why would "reopen windows, or adjust mouse scolling" fix an issue with the video ram.

It may help to discover that I'm able to watch the streaming video from Netflix that operates using Microsoft's safelight and have no freezes. Any flash however will result in a kernel panic and make my mac meltdown.

I'm at the point of considering just selling the machine or installing Windows 7 and making that my fulltime OS as it has no issues at all with such a simple task as playing video.

To those considering buying an Imac RUN don't walk away from them, you are in for **** if you purchase one.

Hi, if you check back to the start of this thread I had this issue with a brand new iMac mid 2011 out of the box with lion pre-installed. I went through all the rubbish Apple ask you to do to detract from the real issue. Nothing worked for weeks and I even got the iMac replaced which also had the same issue. I am a vanilla user I dont have anything installed that wasn't installed from new.

I was at the end of my tether given I had forked out nearly £2k on a machine I thought would be free of this sort of bollocks.

as soon as I applied 10.7.1 this issue was fixed, but for more adventurous users it clearly is still there.

Apple need to sort this as it looks like a widescale Lion compatability issue I have not seen the like of since Windows 98.

Interestingly if you call apple they will 'never have heard of this issue' and tell you they don't have access to thos thread.

Good luck

I have OSX Lion 10.7.2 (iMac 27") with 4850 and I still have problems with video artifacts, the Mac freezes and the only thing that works is the mouse, but I can notpress anything, I just turn off with the button .

I'm surprised that this thread is still going. Last summer is when I had this issue~ now with all the updates, I've had ZERO problems with iMac. I mean nothing since the FIRST patch was placed.

I'd just like to chime in and say that I too am affected by this problem. I bought my 2011 21.5" iMac the week they were released (I should have known better...). In my case I notice that I will also get blue screens related to the ATI drivers on Windows 7 in bootcamp in addition to OS X freezing, Of course, Apple was not aware of the issue when I took it into the genius bar and I couldn't reproduce the problem in the 30 minutes I had to talk to the genius...
They kept it for a week and eventually replaced the ram--which didn't help. I have a thread detailing my experience here.

At this point I am ready to sell the thing.

The reason your new 2011 iMac was freezing as soon as you bought it was not due to a hardware issue, but it was because it was running Snow Leopard (OS 10.6).  Looking at your thread you posted a link to, it appears you purchased the machine last May (before LION's release).  Some users (including me) began experiencing the random freezing problems with later updates of Snow Leopard (probably beginning with 10.6.6).  The freezing continued with LION and has not yet been fully dealt with by Apple.

It appears that a graphics driver bug was introduced in Snow Leopard, though many people do not appear to be affected by it.  I am surprised that new machines have trouble with SNow Leopard out of the box.  I use a 2008 iMac that shipped with Leopard (10.5), so I presumed that my older machine's hardware was to blame. 

My only work-around has been to re-install Leopard.  That is, unfortunately, not an option for people with newer iMacs.  It's disappointing Apple has not at least acknowledged the problem exists.

I am currently prepping a spec for a new 2011 27" iMac with the i7 series chip. Have these issues been resoved with Lion, or are the problems still outstanding? Obviously no point in jumping into the fray with a brand new machine that is still having video problems after an entire year of troubleshooting.

DylanRhea,

The problems with LION have NOT been resolved.  Buying a new iMac would be very risky.  Your entire display will freeze (even the clock stops) and the keyboard & mouse are unresponsive leaving you with no control.  You must then forcibly turn off the machine by pushing the power button--an action that will eventually destroy your hard drive.

Many Mac users continue to report this problem, so it is probably best to postpone your purchase until Apple provides a solution.  I hate to say that I am beginning to lose faith in the company.  It's 5 months since LION's release, and they refuse to acknowledge that there is a problem.

Very very disappointed to hear that. I am replacing a none too old MBP that met an untimely death at the hands of a glass of champagne, and the iMac is really what I was banking on. Does this problem appear to affect the i5 chipset as well?