Norton Task Notification slide-ins disappear immediately

A couple of days ago, my Norton Task Notification slide-ins began to disappear almost instantly. Occasionally, I catch one out of the corner of my eye, but it is gone before I can see what it says.

 

Norton Task Notification is turned on; I tried turning it off and back on, without results. Otherwise, I have not changed any settings. I have not seen this behavior before.

 

The system is NIS 2012 on Windows 7.