Thanks for your response.
I only experience this error in FSX:SE and only after installing the FSDT add-ons. I use add-ons from AS:NE, PMDG, EZDOK, and Aerosoft, and UK2000 scenery products with no issues like this. It may be a Windows error but it only happens when couatl.exe is running and when XPOI is enabled. I have never seen a Guard Page Exception error before. Re-installing Windows seems drastic and, to me, a very last resort. My PC operates fine otherwise.
Here are some details after several flights trying various tweaks such as eliminating services, anti-virus, running as admin, etc...
The error kept re-occurring until XPOI was disabled. With XPOI disabled, I made successful flights to any airports, including the 2 FSDT (Zurich and Geneva) without the issue. With XPOI enabled, the error occurs about 10 to 45 minutes after take-off. I left the plane idling at the gate for 60-90 minutes, and did not get the error. When it does happen, I terminate couatl.exe and FSX:SE continues - no problem, but all FSDT add-ons (only) are no longer available until FSX:SE restarts. It may happen sooner when there are many POI’s in the flight path (quick flight from Gatwick to Heathrow over London).
It would seem there is something about the way XPOI and couatl.exe interface with Windows that is causing the problem. The 2 airport add-ons and GSX trial version (if it makes a difference) also use the couatl.exe interface/program, correct? The airports can be enabled and the error doesn't happen. I would like to have the functionality of XPOI, but if this can't be resolved I will just delete/disable it. That would be disappointing because I do like the add-on.