Hi All,
I've had my own experience with this problem, which I solved for my situation partly because I read all 17 pages and got ideas. So I wanted to share what I learned so that some of you might benefit. Others may not, becasue it's obvious that what worked for some doesn't work for all. Also, I wouldn't rule out a role for superstitious thinking and coincidences as well.
I'll try to be concise and brief.
I have a late 2008 2.53 GHz 15 inch MBP with 4 GB of RAM, and the video is NVIDEIA GeForce 9600M GT 512 MB. This machine has been through a number of system upgrades and inherited data via migration from several previous machines. I have never done a clean install, so there are lots of possibilities for troublesome things hanging around on the disk.
I use it as a desktop with an external monitor most of the time and then disconnect it and take it with me when I travel. Until last year I used it with an older Apple Studio Display from 1999 without any problems. In order to do better photo editing I upgraded to a 24" Eizo CG223W with 1680x1050 resolution. It is connected with a minidisplay port to DVI converter. Again, no problems.
Earlier this month, having already upgraded to Mountain Lion, I installed the 10.8.2 update. Shortly thereafter I began to notice bad behavior, first problems waking from sleep and then, much worse, worsening slow performance so that I spent a lot of time looking ar beachballs or even just waiting while staring at nothing.
I made a short trip and took the laptop with me. In the hotel room it ran totally normally, although it still had the waking up problem.
When I came back I reconnected and began going through many of the steps recommended in this thread and others. That included going to Safeboot and repairing the disk (there were some issues), resetting nvram twice, and then resetting SMC by taking the battery out and holding down the power button.
When I reconnected to the external monitor I was unable to get the display to work correctly. First there was an annoying flicker that made work impossible, then intermittent blanking out, and then mostly a blank screen with the monitor indicating there was no signal. But when I lifted the lid and checked display preferences the computer knew the monitor was there and allowed me to change alignment and so on. On a tip from this thread, I reset the resolution on the external display down two steps, which put it below the resolution of the laptop's screen, and the monitor went on, functioning normally. However, that was unacceptable for photo work.
I was pondering doing a clean install but it's a lot of trouble, I was worried about a backup miscue, and there were messages to the effect that it didn't solve the problem anyway.
After a couple of days of stewing and trying different things, which if anything made it worse, I was reading the messages about gfxcrdstatus. A light bulb popped up in my head about something I dimly remembered seeing. I went to energy saver preferences and under battery there was a choice of two options under "Graphics," Bettery battery life and High performance. Guess what? The first was selected. When I changed it to higher performance and then reset the Eizo to its full resolution I was rewarded with a crisp, clear high def screen as I had enjoyed before all this mess. This was basically, I presume, the same thing that gfxcrdstatus does. Two days have gone by and it remains normal. Also, the slow performance was totally fixed and everything is fast, maybe more so than before. As an aside, I reset the sleep parameters to default and that problem is resolved also - the sliders for screen and computer were different; perhaps that was the problem there.
Hope this helps somebody out.
Ed Merrin
