On Mac OS, the standard way to open the preferences window is selecting the "Preferences..." option in the menu group that has the same name as the program, having the default hotkey cmd+,
In texstudio 2.4., this option exists, but when clicked, nothing happens.
The "Configure texstudio" menu item in the "Options" menu works however.
I would expect the same Configuration window to open for the click on both menu items.
I use TeXstudio 2.4 on MacOs X 10.6.8.