Have you been crashing quite frequently, and your using Apple's Mac OS X 10.6.4 system software with Adobe Photoshop CS4 or CS5?
Apparently Apple introduced updated video graphics - card drivers with the 10.6.4 update. This update may have bugs that lead to display artifacts like fractal looking patterns, intermittent flashes, scrolling, and random vertical or horizontal black lines.
There are a couple of proposed solutions that seem to help.
One, is to run photoshop in 32 bit mode. Select the application, get info and select open in 32 bit mode. (CS5) The good part is, your third party filters will run in this mode as well. The bad news is you just lost a fair amount of speed increase. (If your memory is decent +4Gb or more)
Another fix that appears to work is adjusting the Open GL settings.
Under Photoshop/Preferences/General or Command-K
De-Select the Enable OpenGL drawing function. But wait!
Doing this also limits certain neat functions and GUI options. I suggest first setting it to "Basic". If your still crashing, disable it. But just so you know, your going to lose some functionality as well as "handling traits". See Adobe supplied list below.
Another proposed fix is to revert back to 10.6.3, and wait for the fix. Are you serious ?
One would have to re-install system software, starting from the most recent complete version you happen to have. For most, that would be going back to 10.6 or 10.6.1, 10.6.2, 10.6.3. Then re-install all the updated print drivers, applications, cha cha cha. No friggin' way. (Unless you have infinite time on your hands, and like to watch progress bars)
If your crashing quite frequently, I suggest you follow this course.
If your running third party filters, such as Nik's silver efex Pro, you'll need to be in 32 bit mode. From what I can tell, those in 32 bit mode are crashing less. If your still crashing, set the OpenGL mode to Basic. Still crashing, disable. Still crashing, go back to 10.6.3 and wait for an update. (I'd rather throw my computer out the window)
If your not running third party filters, keep running in 64 bit mode. Set OpenGL to basic. Still crashing too frequently, disable OpenGL. Still crashing run in 32 bit mode with OpenGL on basic. Still crashing 32 bit mode with OpenGL disabled. Still crashing, go back to 10.6.3.
I was in Photoshop CS5 for 12 hours yesterday. I was running in 64 bit mode with OpenGL on Normal setting. I crashed 3 times. Usually I got one flicker as a warning, knowing it was time to save quickly, but not always. More often then not I had a few files open.
I hope this helps until we get an update from Apple. If you have a fix or some input, drop me a note or comment. Happy Photoshopping.
*Update. I've switched my Photoshop to CS5 to 64bit OpenGL on Basic, knock on wood, I have yet to crash today, and I'm 10 hours in...