Reunion crashes as soon as I start it.
When Reunion crashes on startup, it's usually an indication that a preference file has become damaged. To fix the problem, you'll want to delete your Reunion preference files. You can find them here...
You may need to scroll down the contents of your Preferences folder until you see the Reunion preference files. You can then drag them to the Trash.
After you've trashed those files, you can start Reunion again. This should take care of the crash.