I saw another thread discussing this problem marked as "Resolved." Does anyone have a solution that isn't "The problem mysteriously resolved itself?"
A popup appears with the message "Norton Internet Security is Preforming Background Tasks" and interrupts the screensaver. It also keeps the computer from going into power save modes. It does this on multiple third party and windows screensavers (so far, on all that I've tested). I'm not going to turn off background tasks because that is a temporary solution. A full system scan runs in the background every week and has completed. The only correlation I can find is that at the same time these messages pop up, an entry appears in the log that a program was attempting to and was allowed to access the internet. I don't know if they are related.
I'm running XP with SP3.