Single Application Mode

Hey Guys,
I recently reinstalled Snow Leopard and updated to 6.8
I like to think of myself as more than a novice user, and I have installed an Snow Leopard before but I am having a very strange issue.

So I'll paint the picture as follows. I open a forum using Firefox talking about and issue I am working on in Xcode. I want to read the forum with firefox running in the background and have xcode on top so i can read the forum and type in xcode at the same time. This has always been something I could do in Mac osx but currently when I switch applications using cmd+tab it hides all other applications but the one that I have switched to. It is INCREDIBLY frustrating.

I have done some research into this before posting and I have found that since the original osx release there has been an option called Single-app mode. Which does what what I am describing. I have found a terminal command that should turn this off.
First I type this line
defaults write com.apple.dock single-app -bool false
then
killall Dock

Which is what I am supposed to do but it won't work. I have tried this and then restarted my computer and nothing is working. It is incredibly frustrating not to be able to cross reference firefox while coding.

PLEASE HELP!!!