Screen not rendering properly.

I am using a 13" MacBook Pro Early 2011, 2.3 GHz Intel Core i5, 16GB, Intel HD Graphics 3000 512 MB and I have it hooked up to an older 21" Apple Cinema Display. The issue that has recently started occurring is that the cinema display occasionally shows lots of tiny blocks of parts of images, cmyk bars, black boxes, kinda all collaged together in horizontal bands as I move from window to window. Any thoughts? Display going bad? I just installed a brand new battery recently, too.