Big-T,
I had a similar problem to yours with my FSX Gold Edition.
My computer would "type" the letters SSSSSSSSSSSSSSSSS.
This was on my 8 year old Dell i5 3.2 GHz.
I can tell you that my problem occurred more than likely due to an OOM issue. (Although I never was really sure).
I can tell you that it certainly was not an Accessibility issue.
I can tell you it certainly was not a keyboard issue as I am using the same keyboard on my new machine which is way more robust than my old one. I have not had that issue since.
I assume you to be a knowledgeable user as you have been simming since the 80s.
Your machine seems to be robust enough to not suffer from OOM issues but it still is not out of the realm of possibility.
Your use of heavy resource use add-ons MIGHT suggest that.
These are suggestions and may or may not be the remedy but most likely would be good to check.
1. Are you using the HiMem Fix and affinity mask tweak in your config?
2. Have you tried FSX without EZ Dock?
3. Have you tried System restore to a restore point before EZ Dock.
But beyond that I can not offer much advice. But I am interested in how this progresses.
Good luck, Joe