Recreate Steps:

Destroy a 1x1 block area and place water.

Next to it, place a grass block.

Then behind facing you, place any block where the grass is. (For Instance, Stone or Glowstone.)

On top of the stone, Place two pistons on top of each other facing you.

Behind the pistons, place stone (or any block) up to the level of first stone and first piston. (2 x 2 block of stone)

Place a repeater on top where the top of the second piston is located.

Place redstone dust on the second stone connecting the repeater.

Place a lever and don't activate it yet.

Place 3 tall sugarcane on the grass block.

Activate the redstone.

You'll should now noticed the 'Top Piston' has an extended piston and shouldn't be doing that and only does this with Sugarcane I've noticed.

I don't know of this is a 'Bug' or something in redstone has changed to cause this, but I figure I'd submit this anyway and see if you can confirm this or not.

If this is a bug, this it works on Single Player and Multiplayer tested on 1.3.2, 1.4.2 and 1.4.3.

I've created a Single Player World in 1.4.3 demonstrating, If I were to make a massive farm and "How it works".

Mirror 1: https://dl.dropbox.com/u/61261837/Testing.zip
Mirror 2: http://www.mediafire.com/?i2i6zo29ibb5qu7

It's clean:
https://www.virustotal.com/file/acd40c5c570dec11123202782efb825e693cd0198e09b3cb60fed348e2b04567/analysis/1352123709/

Video: http://www.youtube.com/watch?v=gsnuPuHafaw

Again, if this is not a bug I apologize and I'll just use a "Sticky Piston Method" just figure this was going to bug me until I submitted this and know for sure.

Regards,
Cory_