I created a new, single player, superflat world in Minecraft 1.7.2 in creative mode with cheats enabled, the default world (bedrock, dirt, dirt, grass), no seed in the generator, and the bug happens when generate structures is either on or off. I have not tested this in other game modes.
The first time I put a redstone torch into my hand, all the block textures became black, including the item version of the block in the creative inventory. Items were unaffected and it didn't happen until I put the redstone torch into my hand. Saplings, mushrooms, seeds (all kinds), and sugar cane all lost textures in-game and in my inventory.
Changing the "Super Secret Settings" did nothing to restore block textures.
I have no mods installed in 1.7.2.
Opening the world in 1.6.4 yielded normal block textures. Re-opening the world in 1.7.2 after saving the world in 1.6.4 yielded normal block textures until the redstone torch was placed in the hand again.
Other symptoms include two different background music tracks playing at the same time.
The zip file included is the world file shown in the attached photo.
Final note: the same loss of textures happened in one of my 1.4 survival worlds when I put a normal torch in my hand.