Screen flicker after Lion upgrade

I am having the same issue after upgrading my iMac 20-inch Mid 2007 to Lion this afternoon. I also have an Acer monitor but it is attached via DVI. When attached the monitor will just flicker on then off every 3-5 seconds. If i bring up the display settings page it will show lines across the screen but not flicker as frequently.

I upgrade my MacBook Pro Early 2011 with Lion, yesterday.

My system: Processor 2.3 GHz Intel Core i7 and RAM 8GByte (i have buyed Kingston RAM before check compatibility from official site).

After 2/3 minute my notebook display start flicker, and an alarm sound alert me that they have a problem!

Is a RAM problem? Or a video card problem?

I will try to restore original RAM, but why with Snow Leopard 0% of problems??

Same issues here! Upgraded my iMac (24-inch, Mid 2007, ATI HD 2600 Pro graphics) to Lion yesterday. After the upgrade the second monitor I have attached (CMC 22 W Display) now randomly flickers on and off.

I have unpluged the monitor and rebooted the system as a single screen set up, then re-attached it, changed the arrangement to mirror and back again, messed with the resolutions, basicaly anything I could find to affect the second screen, all to no avail. It's still sitting there, flickering merrily away to itself every few seconds.

This setup was 100% rock solid under Snow Leopard.

YouTube vid of someone else with the same problem here.... http://www.youtube.com/watch?v=u5huP9dwNOM

I have pretty much the same set up that you do, just a different brand of external display. The issues seem to be tied to drawing on screen (the more drawing work there is the worse the effect on the external monitor). I have reported the bug to Apple and refered them to this thread for further details, the radar # is 9817002.

I had colored lines appearing whenever CPU spiked (may be what michaelswan reported, but it would always appear whenever I typed on my Bluetooth keyboard of used my Magic Trackpad, which always slightly spikes the CPU, and then whenever CPU usage went up a lot), but switching from DVI to VGA fixed it. I'm running a mid-2007 iMac with a Viewsonic VX2025wm as a secondary monitor. Switching to VGA isn't ideal, but it's good enough for the time being!

I have 2011 i5 iMac with Samsung Syncmaster as secondary display. After upgrading to Lion I had some major flickering in the bottom third of the external screen. Tried rebooting etc, then changed from DVI to VGA connection and now I get shiver. It doesn't happen all the time but it is very annoying making the display unusable. Please fix it Apple..

I've got the same problem here. MacBook Pro 6,2 (Mid 2010). I upgraded to Lion this morning and I've had this issue about 5-6 times so far. My screen suddenly flashes and then goes black, completely unresponsive, and I have to force a shutdown holding the power button.

When submitting the report to Apple, I noticed by the error details that it was a CPU problem of some sort. I've also read somewhere else that this problem arouses when performing CPU-intensive tasks.

Okay, so at first I thought this was a Lion issue, since it started happening when I upgraded to 10.7. However, it has happened again just now while I was on Windows through BootCamp. I was checking my e-mail and performing some other mundane tasks for about an hour, and while trying to copy some files to an external Hard Drive my screen flashed and went black.

Hardware issue then??

I have pretty much the same setup like yours, except that mine didn't flicker. It sort of "blinked" every now and then when I switch spaces. Changing from DVI to VGA and back doesn't seem to cure it.

I have a flikering screen problem, along with a thin line that spans the top edge of mail and safari (don't notice it elsewhere). Fix it apple!

I am having the same issue with my iMac linked up to our flat screen tv using hdmi. It happened straight after upgrading to Lion and like others have noticed the flicker gets worse when the screen is more active (video/flash). I have tried running on windows through bootcamp and all is well so has to be an OS issue. Please fix it or at least respond!😟

Apple does not generally respond to discussions on this forum. I have filed a big report with apple and am working with them to arrow down the problem so they can fix it in an update. The best thing you can do for now is to use VGA, it seems people are having luck that way, drop to single monitor for now, or roll back your OS until a fix is available. When the issue has been fixed if will likely show up in the release notes so just keep an eye on them.

I have an iMac with an external Acer display. I also had the flickering problem. I changed the resolution to 1360x768 which seems to have solved the problem. I have not had any flickering for the last 10 minutes or so. The resolution is much lower, but at least it doesn't drive me nuts! I am also hoping that Apple comes out with a fix very soon. My SL setup worked wonderfully.