My earlier "report" was giving you all information on my findings between the two computers.
No, you haven't. You only gave a report of the files related to GSX, that would be only useful for you to check if some file that came with GSX was missing/corrupted but, of course, a reinstall would have fixed this, it's not the installer "forgets" to install files, they are supposed to be identical, if you install GSX on two different systems.
The files between the two are mirror images....one works, the other does not.
That would be enough proof the problem is not the files themselves, but something outside of them.
Which goes back to my initial question and title of this topic asking is there a compatibility issue with windows 8.1? If others are running this using 8.1 then that answers the question.
If nobody reported it so far, I can only assume that either nobody except you uses GSX + Windows 8.1, which is extremely unlikely, or there are no known incompatibilities, which is far more likely than you being the only GSX user with Windows 8.1. Note that, we clearly indicate Windows 7 as the only supported OS in the GSX Web page. Which means, we'll try to help, but can't guaranteed it will work. That's why we have a Trial version for.
So, assuming it's not the antivirus, you can activate the Simconnect diagnostic mode to see what's wrong with your install:
Open notepad, and copy the following text:
[SimConnect]
level=normal
console=1
RedirectStdOutToConsole=1
OutputDebugString=1
; file=c:\simconnect%03u.log
; file_next_index=0
; file_max_index=9
Save the file as SIMCONNECT.INI in this folder:
Documents And Settings\YOUR LOGIN NAME\Documents\Microsoft Flight Simulator X Files
At the next FSX launch, you should see a text window with diagnostic message, that should tell what's going wrong. Let me know what you are getting, so we can have an idea what's happening.
Only the first few lines are important: if the window scrolls too fast, you can use the "Pause" key on the keyboard to pause the scrolling. Post here only the first 10 lines or so of the diagnostic, but it's important you post the first 10 lines.