One change in 10.6.x was that Apple added new behavior to the Dock’s contextual menu. In 10.5.x and earlier, when you clicked on a program’s icon, you’d get a contextual menu with that program’s Dock commands, along with the OS X system commands (Hide/Show, Quit, and Options).
In 10.6.x, clicking and holding on an application icon in the 10.6 Dock invokes Exposé for that application. This is the same effect you see when pressing the F10 key in 10.4.x and later.
I personally found the new behavior aggravating, especially since my long-established habit is to use the Mail dock contextual menu to select “Get New Mail”. In 10.6, I found that I was launching Exposé instead. I could get the old contextual menus back by doing a Control-click on the dock icon, but I kept looking for a way to get the old behavior back.
Fortunately, somebody has found it. Here’s how you tell the Dock to use the 10.5.x-style dock contextual menu:
1. Open Terminal
2. Enter defaults write com.apple.Dock show-expose-menus -bool no and hit Return.
This change will take effect the next time that the Dock starts up, so if you want to automatically restart the Dock after applying the command, here’s the command you enter into Terminal:
defaults write com.apple.Dock show-expose-menus -bool no; killall Dock
