24" LED Display with 2011 15" MPB

Yep, I'm experiencing the same issue. I just purchased a 13-inch MacBook Pro i5 and I'm getting momentary black screens and intermittent, rapid horizontal shifts when connected to my 24-inch LED Cinema Display. The issue does not occur with my previous 2009 MacBook Pro. I don't have an answer for you. I've tried all of the usual things— reset SMC and PRAM, repaired disk permissions, etc. Very frustrating.

Same here. 24" LED display on my late 20078 MBP never had any problems.
Yesterday I've received my new i7 MBP (faster GPU) and it has turned black for half a second at least 30 times now. Sometimes a get a horizontal bar of something similar to black and white static noise the height of an iPhone in landscape mode across the screen. The internal display is not affected.
Let's hope for a quick software update.

PS: The problem is (sadly) not related to GPU switching. Disabling the automatic switching in the Energy Saver preference pane didn't help. I also can't anything strange in the log files.

We experienced a flickering with the old MBPs when the backlit is dimmed down. It happens only if the MBP is powered by the display. See this post: http://discussions.apple.com/thread.jspa?threadID=2669791&tstart=0

It looks like the linked thread is about flickering (changes in brightness) while this thread is about the display going completely black. It also happens when only the Mini DisplayPort connector is plugged into the Thunderbolt port (no MagSafe and USB connection).

I am having the exact same problem. The screen (on my 24 inch display) is going black intermittently. I seems to get better if I am using both screens instead of just the display.

Count me in. Same issue for me.

Everybody having this problem: please don't forget to post a bug report to https://bugreport.apple.com/ to make Apple aware of this. It only takes 5 minutes.

I do have the exact same problem with both a MacBook Unibody (2008) and a Mac Mini (late 2009), the screen goes intermittently black and returns to normal in about 1 - 2 secs.
It's a quite rare phenomena, and it happens that it can work for multiple hours without showing this phenomena once, and at other times the phenomena can happens multiple times in less than 1 hour.

It may happens more often with latest MacBooks, but it's not a new phenomena.

EDIT: I've read a bunch of new testimonies on a French website that has relayed this thread report, and multiple users report experiencing this issue on multiple models of Mac, including MacBook Pro 2009 and MacBook Pro 2008.
According to one of them, it only happens when the MacBook Pro is used with the integrated graphics chipset (9400m or 320m on older models). I don't know if it's possible to force the new MBPs to use only the dedicated graphic GPU (Raddon HD), but it's something to try to see if the issue on the new ones is also happening only when used on the integrated chipset (intel).

I'm using the discrete GPU on my 2011 MBP. The integrated graphics can't drive an external display apparently.

gfxCardStatus comes in handy to check the currently used GPU: http://codykrieger.com/gfxCardStatus

Of course integrated intel graphic GPU does support external display, how would 13" MacBook Pro would be able to use external display if it weren't the case?

As of gfxCardStatus, did you update to 2.0.1 version? This update is required to have full and accurate support of the new 2011 MBP.

The observation of the user on 2008 MBP is when the GPU is forced to either integrated or discrete GPU, as 2008 MBPs don't have automatic GPU switching. So if that's possible, it would be interesting to force the GPU to discrete GPU manually, meaning making sure the MBP can't switch back to integrated one automatically. As the automatic switching mechanism can have a role to play on this issue, disabling it all together, if possible, would allow to eliminate this factor from the equation.

When running the integrated graphics and plugging in my 24" LED CD the MBP switches to the Radeon chip before activating the Cinema Display. gfxCardStatus also displays the CD as a dependency for the Radeon GPU.
When forcing the integrated graphics through gfxCardStatus, my CD is switched off.

See also: http://codykrieger.com/gfxCardStatus/faq#ext_display

Ok, understood, I didn't know that limitation on dual GPU models with Intel integrated GPUs.

So according to your experiences, you confirm that you still have the screen going black intermittently when selecting the Radeon only mode with gfxCardStatus? I mean forcing it. The fact that it does switch to Radeon automatically when connecting an external display, doesn't really remove the automatic switching out of the equation, it may be buggy and the intermittent black screen could perfectly be because of this process trying to switch back to integrated GPU.
But if you do still experience this issue when Radeon only mode forced, this would allow to remove that process (automatic switching) from the equation.

Good point.

I've now set gfxCardStatus to use "power source-based switching" and forcing the integrated graphics on battery power and the discrete when plugged in.
(This is also useful because some apps force the discrete GPU [even on battery power] unless you use gfxCardStatus to force the integrated graphics: http://codykrieger.com/gfxCardStatus/faq#applications).

Graphics switching is also disabled in the Energy Saver preferences. I'll report back after the next black screen :/