Norton AV Definations **Never** Updating..., Why??

So first let me say that IT is what I have done for a living for the past 20 years, so I am reasonably computer literate, but this issue has me baffled (and a bit frustrated).

This relates to my Home Network which, as background, info, is a hard-wired (not wi-fi) network consisting of four (4) fairly powerful machines all running WinXP-Pro connected through a Cisco router (Dual WAN) to Comcast via two (2) separate and distinct incoming Comcast HSI connections (cables/modems) which each, of course, having separate IP's.  The router has port forwarding properly configured for each of the local machines and each one of the four (4) LAN IP's/MAC's is "bound" to one or the other of the WAN IP's (meaning that they are not randomly bounced back & forth between the two (2) WAN/HSI connections),  There are work-related reasons for this slightly atypical home network setup which are not important to this discussion.

I have always used Comcast's Security Suite on each of the four (4) computers because..., well..., it doesn't cost anything.  I made the transition (concurrent with Comcast) from McAffee to Symantec/Norton some time ago using the proper Removal Tool(s), of course.
By-the-way, McAffee **really was horrible** so, thank heaven for Comcast's transition to Symantec!!


Now to the actual issue:

On three (3) of the four (4) machines I have no problem/issue at all.  However on the fourth machine, despite the fact that it is configured identically to the others, the Symantec/Norton AV Virus Definitions simply **do not automatically update----ever**.  As a result, every three (3) or four (4) days Symantec/Norton on that machine goes into an "red-alert condition" (for lack of a better description), saying something to the effect that:  "Your Virus Definitions Have Not Been Updated In 4 Days..., etc.".

While in this "alert" state, certain necessary background processes cease to function (I guess "for my protection").  I am then forced to run "Live Update" manually (which works fine) and all is well for another three (3) or four (4) days, until this cycle repeats itself again, ad-infinitum.

This would be a relatively minor annoyance requiring my "manual intervention" periodically except for the fact that I often am required to go "on the road" for work with some frequency.  When I do, I need to leave my Home Network up and running so that I can gain access those home computers (and some of their files/processes) remotely for work-related reasons.  The "suspended state" of the one (1) machine that I am referring to then becomes a real problem/nuisance.

I have already tried completely uninstalling/removing Symantec on that machine and then re-installing it on three (3) occasions **to no avail** so this persistent issue remains. There are absolutely no other issues with this machine which might indicate some sort of "OS problem" on this machine and nothing pertinent appears in the XP "Event Logs".  

Can anyone explain why this is happening on only this one machine and tell me what further steps I might take to rectify the issue?

Two final notes (at the risk of sounding a bit "snarky"):
1.  The stock response of:  "Completely reformat your computer and re-install Windows plus 2TB of software & files...." often given by many people..., (who usually don't know what they are talking about and just hang out in forums trying to sound all knowledgable and "31337" ("elite")..., is ***not helpful***.  Please don't bother.
2.  If you plan to respond with:  "Get a real computer..., get a Mac...", or with, "Dump Windows..., get Linux....", or anything similar..., well..., we all acknowledge already that you are "2-kewl-4-skool" and ***soooomuch*** better than the rest of us (there..., your ego has been stroked) so..., please..., don't bother.


Thanks much in advance for any assistance.