Daylite uses a standard Cocoa preferences file. You will find it at:

Home Folder -> Library -> Preferences -> com.marketcircle.Daylite3.plist

You should quit Daylite before removing this file. (You may want to jot down your connection info (computer, database, username and password), so that you can back into your database once you relaunch).

Once you've removed (deleted) the file, launch Daylite. If you want to get back to that last database you where using, choose 'Connect to Exising Database' on the First Run screen.