Endpoint Protection

A user said the computer spontaneously popped this up on the screen, interrupting his work.

In the control panel, open Symantec Liveupdate. Depending on which version you have you may have some options in there. Also, check their scheduled tasks to see if this is being launched that way.

What is the version of SEP installed ? Also how frequently it is running?
Is it   a managed client or an unmanaged client ?
Is the live update failing or is it completed?

 Is this PC managed or Unamanaged ?
When running a scheduled update this should not be popping up.

Do you have any other symantec program installed in this computer ?

What is the version of Liveupdate installed on this PC ( 3.3 comes with SEPM)
Uninstall SEP delete all Liveupdate folders then install SEP.

Also  go to  HKLM\Software\Symantec\Symantec Endpoint Protection\Live Update\Schedule\Type\continuous LiveUpdate

what is the value set there?.

It is a RU5 client running XP.  The screenshot shows it is definition updates updating
It is a managed client, but everyone doesn't have this problem.
The machine is in the office, so it should be updating from the management server.
The client was updated from MR4MP2 via an assigned upgrade package last week.

There is no key

HKLM\Software\Symantec\Symantec Endpoint Protection\Live Update\Schedule\Type\continuous LiveUpdate

It stops at HKLM\Software\Symantec\Symantec Endpoint Protection\Live Update\Schedule\

Please uninstall the SEP and LU from the machine.
Delete :

Delete the following folders (if they exist):

C:\Program Files\Symantec

C:\Program Files\Symantec Antivirus

C:\Documents and Settings\All Users\Application Data\Symantec\LiveUpdate

And then reinstall SEP