Since Photoshop CS6 was launched, and subsequently Photoshop CC, we’ve seen many complaints of weird visual behavior of the interface.  Here are two scenarios, and possible fixes:

PROBLEM 1: BLACK BOXES ETC

Black boxes that appear and disappear randomly on your images, something like this:

blackbox

Not only black boxes, though.  Sometimes white boxes, or weird blue colors in the Liquify screen, or image disappearing when you draw a crop marquee, etc.  Annoying stuff. Never problems with the image itself, just with the way it’s displayed.

SOLUTION A:  Go to Edit>Preferences>Performance, and click on the “Advanced” button. Change the Drawing Mode to Basic, then restart Photoshop.  In fact, restart your whole computer if you haven’t done so recently.

SOLUTION B:  If Solution A doesn’t work, go back to Edit>Preferences>Performance, and uncheck the “Graphics Processor” checkbox to turn it off altogether, then restart Photoshop again.

PROBLEM 2: TERRIBLE GRAIN
When your photos look awfully grainy or noisy, but when you zoom in to 100% it goes away.

SOLUTION:  Go to Edit>Preferences>Performance, and check your Cache Levels.  You’ll find they’re on 1 or maybe 2.  Change them to 4, then restart Photoshop (or your whole computer if you haven’t done so for a while):

cache

DESPERATION:

If none of the above solutions work for your issue, fill this out then post the results in the forum, along with a description of your issue, or better still a screenshot to demonstrate it.