Out of nowhere today, anytime I open something up in preview... the files appear corrupt? I'm not sure how else to explain it, but it basically looks like blocks and rectangles of color. I've restarted my computer, as that's all I know of what to do, ha! Please help!
To me that looks like a failing graphics card. Not knowing what OS you have, we can't really give you anything to try, as El Capitan is a lot different from the OS before, Mavericks.
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