6 Command Blocks (= fast clock + 100 particles a tick when moving) cannot create enough server lagg to stop redstone from running, can it?
Please confirm on more than 494 MB (The higher, the better).
Also see (sorry, I dont have a better video):
http://youtu.be/yBFETNi8Rlw?t=2m45s
EDIT:
Confirmed a bug. Try this to reprocude:
Step 1: Teleport to 0 64 0
Step 2: Run a command block in a chunk (I guess activating redstone works aswell).
Step 3: Delete the world.
Step 4: Goto %appdata%/.minecraft/saves/<Your save>/region. r.0.0.mca should be in there.
Step 5: Open a new world, called the same name as the old one.
Step 6: Teleport to 0 64 0. The same commandblock/redstone should still be there.