In some rare circumstances the preferences file can get corrupted; this may be the problem.
Try trashing this file (you will need to reset your Doozla preferences again).
1. Make sure you are not running Doozla
2. Find the file ~/Library/Preferences/com.plasq.doozla.plist
(In Finder, use the "Go to Folder" feature - select it from the Go menu with the Finder in focus, then type in the following in the window that appears: ~/Library/Preferences/ -- then look for "com.plasq.doozla.plist" file)
3. Trash this file
4. Relaunch Doozla