Go to your username>library>preferences and delete:
com.adobe.PhotoshopElements.plist
Adobe Photoshop Elements 12 paths
Adobe Photoshop Elements 12 settings
To see the library, click the Go menu in the Finder and hold down the Option key and it will appear below the little house for your user account. While you're in there, go to the Saved Application States folder and delete any for PSE.