Ask on the PS forum.
Moving this discussion to the Photoshop General Discussion forum.
Surely a video card driver problem, although it does look like a blend mode thing. I just did a quick Google and there were several hits about Illustrator/Photoshop blend mode problems
Suitcase has been known to cause file corruption - check with Extensis for updates.
Video card / driver bugs can cause similar issues on screen - but they don't stay with the file, and will change as you move or zoom the document.