Just normally playing through on minecraft testing out all the new things for 1.5, and I've come across this inside a cave.
As you can see in the photo, the blocks "outline" have specs of visual coming out of them.
Environment
Mac OSX 10.8.2, (Latest Version Of Java, I literally downloaded a new update) Computer Specs: 2.93 GHz Intel Core i7, 8GB 1333 MHz DDR3, ATI Radeon HD 5750 1GB,
53rd duplicate of MC-1794, please use the search function to see if your bug has already been submitted. Currently over 54% of tickets are being closed as duplicate.