When you have a piston that pointing up that has a 'block of redstone' on it and you put a piece of redstone next to the 'block of redstone' it will trigger the piston and it will stay stuck, but the piece of redstone will deactivate.
Environment
windows 7 ultimate, java 7, Minecraft 1.6.1
189th Duplicate of MC-108, please use the search function to see if your bug has already been submitted. Currently over 57% of tickets are being closed as duplicate.