I suspect this is a database issue - but I can't seem to find it.
Pop Up 3.1
The Pop Up plugin was working fine prior to a Word Press 3.3.0 (and updated to 3.3.1) update.
After the update it just showed a blank white box. Uninstalled - reinstalled - upgraded to newest version - nothing changed.
Changed PO_GLOBAL to true and was able to edit the pop up and it would display. Reset PO_GLOBAL',false - and it will only show global pop up. I can't get it to work site specific.