I keep getting the popup saying I'm not registered, even though I did registerIn the rare case when this happens, you may need to delete your preferences and start again from zero.
Preferences are files named fr.madrau.switchresx.daemon.plist and fr.madrau.switchresx.app.plist, and are stored in /Users/(your name)/Library/Preferences folder.
(Warning: this folder is hidden on Lion and above, so use the Finder "Go" command to open the Library folder)
Put these files in the Trash these files, and start again
You will have to enter your serial again; the last time, normally.