Deleting Preferences Files
From Mac Guides
Sometimes applications will exhibit strange behaviour, such as unexpectedly quitting immediately after opening. These problems can sometimes be fixed by deleting the application's preferences file.
Preferences files are located in ~/Library/Preferences/, where ~ is your home folder. The name of an application's preferences file is sometimes in the format "com.[company name].[product name].plist", for example iTunes has a preferences file called "com.apple.iTunes.plist". Other preference files are simply the application name, without the "com" prefix. Other preferences are stored in folders with the applications name.
Once you find an application's preferences file, quit the application, delete or rename the preference file and relaunch the application. See if the problems continue. You could also try finding other support files that the application uses by searching for files containing the application's name, especially those located in your user's Library folder.