It's likely a problem caused by the antivirus, that has blocked some downloaded files, but let pass others, causing a version mismatch, which will cause a quit to desktop.
Try to reinstall the Stand-Alone Addon Manager again, but keep the antivirus off when installing.
After the installation, but before starting FSX, configure the antivirus to exclude the following files from scanning:
YourFSXFolder\bglmanx.dll
YourFSXFolder\Fsdreamteam\Couatl\Couatl.exe
Then you can start FSX.