If you’ve been using Mac OS X Leopard 10.5 or 10.5.1 and had previously used the Terminal to make your menu bar opaque, you’re going to notice that something is slightly out-of-order when you upgrade to 10.5.2. Basically, what happens, is the old menu bar opacity hack still works in 10.5.2, but it looks slightly odd; and seeing as the update has the functionality built right in, you might as well just revert the hack.
Reverting the hack is simple. First of all, open a Terminal (/Applications/Utilities/Terminal.app) and in the console type the following commands:
sudo defaults delete /System/Library/LaunchDaemons/com.apple.WindowServer 'EnvironmentVariables'
sudo plutil -convert xml1 /System/Library/LaunchDaemons/com.apple.WindowServer.plist
sudo chmod 644 /System/Library/LaunchDaemons/com.apple.WindowServer.plist
This will delete the hack parameter, convert the com.apple.WindowServer.plist file back to a readable XML format, and then reset the permissions on the file.
Once you’ve reverted the hack, restart the computer, and then you can go ahead and upgrade to 10.5.2. If you’re already running 10.5.2, you can change the menu bar opacity option in System Preferences > Desktop and Screen Saver (the nice thing about this is that it is on-the-fly, no need to restart any more).