1. exit virus scanner, turn off ms firewall, scary.
Nobody said you had to turn off firewall. Only antivirus, and ONLY if it mistakenly detects a threat, not if it doesn't do anything. No all antivirus are faulty, most of them just work.
3. run Fsx in windowed mode, checked that both programs were active in addon menu, addon manager and coutl
But did you had the *buildings* at that stage ?
4. inserted serial, went to web page for activation
5. upon receiving registration key, went back to addon manager and pasted key into page
6. after short delay, system replied eSeller fatal error
This is not clear: are you saying you tried the OFFLINE activation ? Why ? Since you said you saw the installer downloading files at the end, it means you have an internet connection so, why the offline activation method ?
This, according to your description of the sequence, which is insert serial, go to the web page for activation and get another code back.
This is the OFFLINE activation and it should't come up if you HAVE an internet connection, the normal procedure is just insert Serial, and let it activate, NOT go to another web page and get another code, which is what you said you did, which shouldn't simply be possible if you HAVE a working internet connection.
It's possible your internet connection was down for a brief time, so the offline procedure come up ?
7. re-ran addon manager, scenery still in trial mode
That's obvious, if you inserted the code for the offline activation in place of your Serial Number, it won't work. If you have an internet connection, you only need to insert you Serial Number, and nothing else, no other web page and no other codes. That would be the offline activation, and it shows ONLY if your internet connection is down.
8. try again - reboot computer
9. setup anti-virus to ignore bglmanx.bgl and coutl.exe
Not needed at all, since you HAVE their menus. This is only required if you DO NOT have their menus.
10. setup ms firewall to allow bglmanx.bgl and coutl.exe
Nowhere we said you should exclude those files from the *firewall*, which is not needed since they don't connect to the internet. If anything, the only file that should be INCLUDED (not excluded) or, better said, ALLOWED to go online, should be FSX.EXE, and NOT with the default MS firewall, which works with our products without needing any configurations.
11. run Fsx and checked addon menu, both addon manager and coutl menu present
This means all works, and there are no antivirus problems.
12. addon manager still reports Zurich as in trial version.
Again: did you HAD BUILDINGS here ? Do you see the "Trial for Zurich has started" when you go to the airport ?
13. went to register again, entered serial key and nothing appears to happens, addon manager returns you back to FsX
This means you entered your Serial Number wrong. Or, you entered it right, but you didn't selected Zurich. You need to enter your SERIAL NUMBER, which is the code listed as "Serial Number" on your purchase receipt.
14. ran addon manager again, Zurich now reported as active
This is strange and it simply can't happen. You said that when you entered the serial when the scenery was in Trial, it did't do anything. That can only means you entered it wrong so, it's not possible it would be active now.
The only possible explanation, is that you haven't noticed the question "Do you want to activate Zurich on this PC", which has been made immediately after the Serial was inserted.
15. loaded FsX at Zurich, took off out of zurich 8fps, ok wasn't expecting that hit BUT BUILDINGS WERE PRESENT ON TAKE OFF. p.s. I get 30fps out of sydney.
That shouldn't simply happen, nobody has ever seen that fps on Zurich, I get about 40 fps on my system, this means something very wrong is in your FSX installation.
But, at least, at least you had buildings, which means everything works.
16. fly out for a while and turned around and flew back to Zurich airport.
17. NO BUILDINGS PRESENT, huh, no messages about time trial running out, so i check addon menu 
18. coutl menu present
19. bglmanx menu present, opened addon manager and Zurich still reports as active.
This shouldn't simply happen. If it's active, then it's active, and building shouldn't disappear.
This is what has happened for ZurichX, Honolulu, Hawaiian Airports 1 & 2, they just don't work.
This has been a very complex setup procedure using up a lot of time and effort for something that is usually easy, ie buying new scenery and installing into FsX.
You made it more complex that it is, there's no special procedure, just install the scenery, select "Register Serial", let it activate and it will work.
If you passed through the offline activation, it's of course more complex, but that's not obviously a problem of the scenery or the installer, it's just because your internet connection was down at that moment, since the offline activation method doesn't appear if the internet connection works normally.
I did see something about AES ?? on the forums what is it and does it have an effect.
It's an Aerosoft product and, if you don't know what it is, you shouldn't have it installed on your system so, it shouldn't be related to any of this.
So, all your points but, in fact, your only problem is that everything works at Zurich (although at slow fps, which is not surely a problem of the scenery) and you don't have buildings when you go BACK ?
Check if you have a Couatl.ERR file in the following folder:
%APPDATA%\Virtuali
