I've experienced this bug before, back in beta.

This is not the old floating torch glitch. The torch flies around erratically really fast like a mad bee.

Most often occurs when I'm placing torches in a dark cave. You only see it for half a second & it pops up randomly. Ir kinda reminds me of the Crazy Lamp Bug glitch from Assasin's Creed. Watch the lamp; that's what the Minecraft torch does. http://beta.xfire.com/video/24c1c9