Go to your username>library>preferences and delete:
com.adobe.Photoshop.Elements.plist and/or com.adobe.PhotoshopElements.plist
Adobe Photoshop Elements 8 settings
Adobe Photoshop Elements 8 paths
Opera preferences (if you have it)
If you are using 10.7 or 10.8, that particular library is hidden. To see it, option click the Go menu in the Finder. It will appear below the little house for your user account. Also, in 10.7 and 10.8, while you are in there, go to the saved application states folder and delete any for PSE.
In all versions of OS X, repair permissions before using PSE again.