First off this bug happens in both creative and survival mode. I was experimenting with making a redstone timer with the new redstone block, and when I started surrounding a redstone lamp frame with black wool, this annoying bug happened. On the edges of the black wool and redstone lamps, you see lines, or i would call "incomplete textures". I will attach some snapshots to this bug report. They look like these sort of white lines surrounding the perimeter of the blocks. This also happened with redstone torches. Around the torches block radius, you would see those lines there. They are kind of hard to describe but it will be clear in the pictures. The first time this glitch happened was when i imported my 1.4.7 test world into the newest snapshot. But the same thing happened when I tested it on a new world generated by the snapshot.
IMPORTANT: MAKE SURE TO MAKE THE PICTURES I ATTACHED BIGGER BECAUSE THE LINES ARE NOT SEEN WHEN THE PICTURE IS REALLY SMALL. THE LINES ARE MORE VISIBLE IN THE FOURTH PICTURE WITH THE SINGLE REDSTONE TORCH.

Ways to reproduce
1. Put down at least 2 black wool blocks next to each other and look in between them.
2. Put a redstone torch down. (Onto a dark block preferably so you could see the lines). Look on the bottom of the block and around the torch.
3. Put Black wool next to redstone lamps and look between the blocks.
4. There may be other ways, but I don't know of them.