...$0.02
I haven't seen that specific issue, but I've seen others that have caused me to re-install. Since you've already done it 5 or 6 times, here's what I did.
I use a Dell 610 laptop to run AHP (with all plugins) for my cameras. (I can't get VA11A to work with my Vista desktop)
1. Reformat
2. Load XP PRO
3. Load NOTHING ELSE until XP has repeatedly updated itself to SP3 and when manually running UPDATE, nothing shows up. (all updates & patches are applied, including IE7) - This took at least overnight, and I was connected to Internet from the start.
4. Do NOT use OneCare or Defender
5. I loaded Symantec Antivirus
6. Then I loaded AHP and all the modules - I didn't plug in the VA11A or the CM15A until it instructed me to do so. I did NOT enter any registration codes, nor use AHP in any way until all plug-ins were loaded. THEN I entered all 5 registrations codes at once and let her rip.
7. Then I rebooted.
Run TASKMGR and see if X10NETS is loaded.
I don't know why, but sometimes I have to reload iWitness to reset the VA11A. Running the X10Drivers.exe doesn't cut it.
IF you load any other software, keep track of when X10NETS throws the error, then uninstall whatever you just loaded & see what happens.