When you switch your texture pack in game, the textures of already loaded chunks are messed up in tell a block is change in the chunk or you go away from the chunk and go back to it (basically refreshing the chunk)
I don't know much about programming and stuff but if you made it so the chunks reloaded after switching the texture pack, wouldn't that fix it?
I put up a video of the glitch on YouTube
http://www.youtube.com/watch?v=FoqXmEY8Kmc&feature=youtu.be
Duplicate of MC-7627, please use the search function to see if your bug has already been submitted. Currently over 45% of tickets are being closed as duplicate.