Update: I found my problem and it was NOT Norton Security Suite! My apologies!!
It turned out a startup application to do back-ups, RetroExpress HD 2.5, was the culprit. More on this below. I isolated this in the following way:
First, I disconnected my PC from the internet and removed Norton Security Suite entirely. That did not solve the problem. The screensaver still did not function properly without Norton. That got them off the hook!
Next, using msconfig, I disabled all non-Microsoft processes and all startup programs. Problem went away! Then I restored all processes and the problem still went away. That cast the suspicion on the startups.
I then systematically disallowed startup programs. The last one to go was RetroExpress and when it was disallowed, the problem vanished. Then I re-enabled all startups except RetroExpress and the problem remained solved.
I shouldn't have been so quick to blame Norton but it was a recently added application. My mistake was not realizing I had also recently upgraded RetroExpress.
Checking on the Retrospect site, it turns out this is a KNOWN problem which EMC attributes to bugs in the Microsoft .NET framework that it uses that are manifest on some PC installations. Another symptom on some sysmtes is that the RetroExpress application seizes scren focus. EMC has no solution! So, today, I'm writing Microsoft Backup scripts. Bye-bye Retrospect!
It was strange: The blank screensaver would work for waits of, say, 1 minute but not for 10 or 15 minutes.
Again, my apologies for the red herring.
Norton Security Suite is much faster and less intrusive than McAfee. I also like the controls I have over its operation.
Thanks again to this valuable community feedback service.
- Pogo