I beleive Pixel Bender is from Adobe Labs for CS5 and was dropped. It is not compatible with CS6. http://labs.adobe.com/technologies/pixelbenderplugin/
There is a link to CS4 version on that page may need to follow a few links to get to the actiual CS4 download.
Pixel Bender requires CS5 Extention Manager....
I have the CS4 download, but correct me if I'm wrong, you're saying I need the CS5 extension manager to make this work?
That is what is written in the link I posted please read them