Why does my iTunes dock icon keep turning semi-transparent?

Like this?

Exactly.

You are hiding the application. Command + H will do this. Or this will do it too.

edit :: I don’t think it does this by default. Have you installed TinkerTool?

Yeah, I should have mentioned that it looks exactly like it would if it were hidden.
That’s where I’m confused. The application is not hidden. The icon is sometimes like that even when I’m playing around in iTunes.

Weird.. I’m stumped. Have you tried restarting?

Yes, I did. I also removed and replaced the icon in the dock.

Also try repairing permissions, and dumping out the cache files for the dock, and perhaps even trashing the prefs file for the dock?...just reaching here b/c I’m not by a mac at the moment.

p.s. Also flash the PRAM (restart while holding down Command + Option + P + R, and keep holding those keys down until you gear the startup chime a second time).

From the Terminal:

Last login: Fri Jul 4 12:09:12 on console
Macintosh:~ whatever$ defaults write com.apple.Dock showhidden -bool no

Kill the dock in Activity Monitor. That could help.

defaults write com.apple.Dock showhidden -bool yes

That will bring back the transparency in hidden apps.

killall Dock to restart the Dock process from the Terminal. JP’s suggestion is most likely the solution. How on earth the setting was changed, I have no idea. Perhaps try using defaults read before you do anything to find out what it’s currently set to.

defaults read com.apple.Dock showhidden

Just tried all of JP’s Terminal suggestions, as well as richardhenry’s, and then some of my own. More restarts. No success.

Perhaps this is just one more wheel falling off of my PowerBook. It really is time for a replacement. I haven’t been able to run on battery power for over a year….

Tried deleting your Dock preferences?

sudo rm -r ~/Library/Preferences/com.apple.dock.db ~/Library/Preferences/com.apple.dock.plist; killall Dock

Just copy this whole code straight into the Terminal and enter password.

Yes, I tried that upon sndfreQ’s recommendation.

Ow, sorry, read over that.

Try creating a new user (or logging in as a different user if you already have multiple accounts) and see if the problem persists there. This is always a good place to start. If it exists in both accounts, you have a low-level system issue. If it’s only in one account, the issue is a setting or preference or corruption in your user account.

Well, since this problem occurred, I have purchased a brand new MacBook :D
Problem solved.