Graphical artifacts in 1.5 prerelease

http://img819.imageshack.us/img819/8905/25700362.jpg

This is a picture of me staring at a stone wall in MC. There are these weird holes in the wall, as if you can see through them, that seem to show the sky, by the looks of it. Happens in both Creative and Survival. Everything was fine in 1.4.7. It seems to be a non common problem, as none of my friends have it.

It's only that bad with stone, the rest of the blocks seem fine for the most part, except maybe the edges a little bit