I've been using PS Elements 6 for about 2 years, and do all my editing and printing with it. I've had my Canon Pro9000MkII for about the same length of time and I've never seen anything like this.
I printed an image and it came out larger than I expected on the paper. I checked and rechecked and the printed image was larger than the onscreen image, by about 1/8" in each direction. It was just a test print so I blew it off. In the process of testing, I made two more prints of the same image, at a different size from the first. Of these two, one printed at the correct size and one was larger. There was more than an hour between the prints but neither PSE nor the printer was shut down during that time.
So I shut down PSE, restarted it and printed a different image. This one is also about 1/8" too large in both directions. (The aspect ratio stays correct.)
I print a lot and I've never seen this before. Has anyone else?