What might cause the following error message?

We are using Norton Internect Security and the On-line Family products on (2) Windows VISTA laptops.  Our children have the standard account without admin capabilities.  They don't know the passwords, etc for the admin account.

 

We periodically receive the following message:

Hi Dad,
Norton Safety Minder plug-in is disconnected or disabled on Howe Family Laptop 1 . To resume monitoring the Internet activities of your children, restart the Web browser or restart the computer. For more details, do the following:

  1. Go to onlinefamily.norton.com
  2. Click Member Sign In, type your email address and password, and then click Sign in.

This is an automated message from Norton™ Online Family. Please do not reply to this email. If you would like to disable automatic notifications for this type of event, please visit the "Notify" area on the "Settings" page and uncheck the options  

 

Any ideas?  Have we got everything set up properly?  Is somehow the children getting around the system?