Mark since 1.8 has just released there are quiet a few bugs. I have noticed in areas around the map that there are random dark patches about 2x2 blocks. By hitting on of the blocks its lights up. So as you might have noticed yourself through your skin, there are some bugs that need to be fixed with the lighting. You have to remember Notch did change how lighting is done especially with torches. Give it a week or so if the problem does not solve itself the either get a new skin or ignore it. Good luck.