We recently ran into a problem where one of our customer's servers was randomly rebooting. It looked like the cause of this was the updates from Backup exec that were being downloaded and installed. We checked backup exec and it was not set to install updates at all. After some research we found that they updates were being installed even though it wasn't set to do so. [more]
We noticed the updates were occurring the same time as the SMSE updates. After researching with Symantec I found that by default Backup Exec is registered with LiveUpdate and is configured to receive updates ANYTIME LiveUpdate is run from ANY Symantec application configured to use LiveUpdate. Thus every time that SMSE started LiveUpdate it would install Backup Exec updates as well. I downloaded a utility (BeUpdateOps.exe) that I used to unregister Backup Exec from LiveUpdate and this stopped the random reboots.