Leopard vs. InDesign: Can't Hide InDesign.
A common Leopard-vs-InDesign complaint we hear from designers is not being able to hide InDesign, either from the InDesign menu or by pressing Command-H. And worse, if you can get InDesign to hide, you can't get it back.
Happily this problem can usually be fixed by deleting the InDesign preference file.
Possible fix: Delete InDesign's preference file.
The quickest way to delete InDesign's preference file is to hold down Control-Command-Option-Shift when launching InDesign. You'll get a dialog box allowing you to easily delete the preference file.
Or if you prefer, you can go into
~/Library/Caches and delete the contents of the Adobe and Adobe InDesign folders by hand. (Note: ~ denotes your User folder.)
Quit and relaunch InDesign, and the Hide option should work again.
Source: This tip written up in the May 2008 issue of Design Tools Monthly.