It happens often that you'll place a block and can't break it. Usually happens around a height of 79. Once we try to break the block, we can place another block inside it. Blocks will also show up invisible when placed sometimes. Not sure if this helps but I'm using Mac OSX 10.6.8 with an intel I3 processor and 16 GB of R.A.M. Running snapshot 14w29b (couldn't find the option for that in versions so i clicked 1.4)

Attached is a switch I placed and can't remove. It is at height 79.