The person in that post seems to have a similar issue, perhaps even the exact same issue and they just didn't realize that the difference between machines that worked and did not work was whether a user was logged on or not. In any case, I'll just try pushing the comm update package in the middle of the day when most users will be logged on, that should be easiest path. Hopefully the subsequent package auto-upgrades will work for logged off machines.
According to this article:
http://www.symantec.com/business/support/index?page=content&id=tech164327
"The installation *should* succeed even when no users are logged on to their computers"
I added the emphasis on "should", as I took that to possibly mean it may not be 100% reliable with no one logged on.