From the screenshot, definitely looks like the video card.
From your system spec, I see 2 video cards. Is this intentional?
Graphics ATI Radeon HD 5770 1024 MB
Software Mac OS X Lion 10.7.5 (11G56)
NVIDIA GeForce GT 120 512 MB graphics
I have three screens.
Two are my main screens for photoshop (each use NVIDIA GeForce GT 120 512 MB graphics)
and the third is for the tool boxes (uses the ATI Radeon HD 5770 1024 MB graphics )
Does turning off »Use Graphics Processor« in the Performance Preferences and restarting Photoshop have any bearing on the issue?
The problem is that the strange pattern wasn't notice until it was saved.
So the 'damaged' on the layer won't disappear..
Have you tried Layer > Layer Mask > From Transparency and then turning off the Layer Mask?