Firefox and Word won't stay in Dock

Can anyone tell me how to keep the icons for Firefox (3.0.8) and MS Word from disappearing from the dock? I keep checking the "Keep in Dock" command, but when the programs close, they disappear again. I've tried dragging the icons from the Finder window, and from the Applications folder. They just won't stay put! MS Powerpoint, and Excel or any other icons I've dragged to the Dock are fine. What's up with that?

Expose,spaces,automator

Sorry wrong thread

Go to your Applications folder and drag a copy of the Firefox icon top the Dock. This creates an alias in the Dock. Just click to open the program. For Word you will have to open the Office folder, and drag the Word icon to the Dock.

I would run Repair Permissions first.

2nd I'd try moving ~/Library/Preferences/com.apple.dock.plist to your desktop
Log out and back in or open up terminal and type in 'killall Dock', without the quotes.

If that doesn't work you can move it back, if it works you can delete it.

(~ is your home folder)

SUCCESS! I have a solution that worked for me!

SUCCESS! I have a solution that worked for me!
I can gladly say the AirPort Utility icon is now staying in the dock. Here are the steps I took:

Some Application Icons Won't Stay in the Dock - Mac Forums

Theses may be of help as well:

Apple - Support - Discussions - Apple Applications won't Stay in the ...
Apple - Support - Discussions - Leopard and Dock Icons mysteriously ...