Mac OS X: The Logger Pro or Logger Lite window is missing, but the menu bar is visible.

There are a possible causes for this behavior:

1. Display settings
The most common way for the main window of Logger Pro or Logger Lite to be hidden is to have the computer configured for two monitors in a non-mirrored configuration. This is easy to accidentally do with a projector.

If you have a second display, test this by disconnecting the display cable from your computer. Your desktop should refresh, and all windows will be visible.

2. Spaces
There is a feature Mac OS X 10.5 and newer called Spaces that creates virtual desktops for organizing your workspace.

It is possible to have Logger Pro or Logger Lite the active application (so that the menu bar is visible) but to have the Logger Pro or Lite window contained in a space that isn't visible. This is confusing if you are not aware that Spaces is enabled.

In Mac OS 10.7 (Lion), Spaces are enabled by default as a feature of Mission Control. Use the F3 key to launch Mission Control, and see if the Logger Pro window is displayed in another Space.

To disable spaces in Mac OS 10.5 and 10.6, go to System Preferences, choose Exposé and Spaces, then the Spaces tab. Uncheck the Enable Spaces checkbox.
Starting with OS X 10.5.4, an option in Spaces is available that forces the OS to switch to a space that includes an open window for the application. If you wish to keep Spaces enabled, also enable this option in the Exposé and Spaces System Preference.

3. Reset Logger Pro preferences
It is possible for the Logger Pro preferences file to become corrupt and fail to display the main window.

If the Logger Pro window cannot be moved to a useable space, try deleting the Logger Pro preferences file, found in the Library folder of your user account:
~/Library/Preferences/com.vernier.loggerpro.plist

The Logger Lite preferences file is found in the same location and named com.vernier.loggerlite.plist

Follow these steps to remove the preferences file:

1. Go to Finder and choose Go from the menu.

2. In OS 10.6 and earlier, navigate to Home, then Library and Preferences.
In OS 10.7 and newer, hold the option key to make the Library visible. Choose Library, then Preferences.

3. Search the folder for "vernier" to find the plist. Copy a backup of the file to your desktop and then delete it.

Additional notes:
A quick way to test if there is a problem with the user or Logger Pro settings is to create a new user in OS X and try Logger Pro in that environment. If Logger Pro works normally there, the problem resides in the settings on the first account. To create a new user, go to System Preferences, and then the Accounts panel. Unlock the panel if necessary, then click the + button, and create a new admin account. Close System Preferences. Log out, and log into the new account. Test.
You can delete this account from your original account after the test.