My 3880 was slightly skewing all my prints from the day I got it. I looked at the mechanism in detail and saw that it didn't look quite the same as my old 3800 (which I still had around). The moving paper guide on the right at the base of the auto sheet feeder was slightly sticking, so it didn't stick out as far as it should and was slightly tilted, and the tilt was causing the skew. I called the Epson repair/support number that came in the printer documentation, and, after talking me through a few checks for awhile, they arranged to ship me a replacement printer under warranty. You might take a close look at your right paper guide and see if it doesn't look right, in case you might have the same problem. (Though I'm not sure you could tell if you didn't have a correctly functioning similar printer sitting there for comparison...)
Lisa