Has anyone seen something like this before?

Canon_T90_008 by Abram Goglanian, on Flickr
(please excuse the terrible scan, I just wanted to show the example)

I ran a test roll through my T90 and on a couple shots that were for sure with the 28mm (not all of them mind you) I noticed these lines. I've never seen anything like this before and I'm just curious what the cause could be.

Any thoughts?