It's a repeating pattern in all colors so I would say something is physically wrong with your fuser.
My guess would be a contaminate got on it (think whiteout), but whatever it is should be visable, and it is entirely possible you may be able to clean it off (but might not). Remember the fuser is hot, let it cool down before touching it.
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I purchased the Xerox Phaser 7100N a few months ago, I have printed less than 100 pages thus far and I just started having this issue today. The prints come out fine at the top of the page, but after about the half way point the page becomes smeared with ink and creased.
I have four pictures on my photobucket. The first one says it all.