Mac crash / Mac blue screen flash during use (not at startup)

A few days ago my MacBook Pro (running OSX 10.6.6) starting having some weird issues. I would be working on the computer, and all of a sudden the screen would flash blue, and then a few seconds later show my blank desktop background, and then finally the dock would come back. All within a few seconds. All of my applications would be closed as if it had restarted.

This has happened about five times, all when I was using different programs. The first time it happened, it was after I dragged a file to trash; after that it happened while using iPhoto and it had frozen up on me; and another time while using Safari. Most recently, the blue screen flash occurred after waking the computer from sleep and trying to close the browser windows in Google Chrome.

I've researched a lot of Mac forums and apparently this is a common problem, and I saw posts from 2007 that were never resolved; I still haven't found a forum with a clear answer.

Anyways, I reviewed the console from the crash this morning, and saw that there was quite a bit of activity all occurring around the time of the blue screen flash, like "windowserver port death" and a whole lot of errors and warnings. This narrowed it down to a possible problem with the window server. I took it in to the Apple store nearby and spoke with a Mac Genius. I showed him the console with the errors, and he suspected it might be a permissions error causing the system to crash and then reboot (looks like it is logging out and then re-logging in at rapid pace).

The Mac Genius attached an external hard drive and rebooted from that and ran permissions repair. He recommended doing this every 3 months or so since it is easy to corrupt permissions. I had never done this before, and it took about 12 minutes. He also said he would recommend doing this at home by booting from the Install DVD I got with the computer. To do this, you have to press the 'option' key during startup in order to have the option to boot from the DVD. (I guess this is a change from pressing "C" with older models.)

Here's how to reboot and repair permissions from the OSX install DVD:

• Insert install DVD, restart computer, and hold down the 'option' key during startup.
  
• This will give the options of booting from the hard drive or the DVD – select DVD
  
• The reboot could take up to 5 minutes or so.
  
• When install screen comes up, go to "utilities" in the top menu bar and select "Disk Utility."
  
• Click on the main hard drive (not the subfolder/partition), and click on "repair disk permission" button, allowing the process to complete. This could take a while, especially if never done before. (It could take up to 3 hours, but mine took 12 minutes.)
  
• Quit Mac OSX installer from the menu bar and restart.
  

We were thinking this should clear up the problem, but if not, the second resort is to archive & reinstall OSX (archive will save all your data), and a third resort is to erase and install (after full backup of all data, of course). We'll see what happens! Hopefully it will work. That would be nice, since it is rather annoying to get the blue screen flash in the middle of doing something, and loosing any data you were working on.  

Update 5/17/11
Well, after many months, many disk permissions repairs and many more blue screen crashes, we decided to go back to the Genius Bar. It was evident that the problem was not fixed. When we returned they ran a test on the hard drive. It apparently failed the test to some degree because they replaced the hard drive. Perhaps it was a hardware problem all along? We'll see.

-- This is a guest post by my wife Susan