This happens when the new Pharos PopUps for Mac version 10.8 is installed in combination with the older 8.1 version of the PopUp package. The PopUp error appears repeatedly, and will generate a new error dialogue box every few seconds.
This can be remedied in 3 different ways:
The fix will be in removing the Popup Login Item from the Users & Groups section in the System Preferences of the Mac as the 8.3 launchd process starts the Popup process instead of the older Login Item method.
Pharos is aware of the challenge, and is working on a solution which will be posted on Pharos KB article 1783