I always runs as administrator, and I do not use any compatibilities.
This sentence is self-counterdicting. "Run as administrator" IS one of the "compatibilities" option. It's on the "Compatibility" tab of the executable for a reason. Try turning it OFF (so everything in that page is turned off), which is how FSX is installed by default.
I do not have any GoFlight hardware or software.
Then the conflict is caused by another addon or a problem with the VC++ libraries. The GoFlight case it's just one example of a conflict caused by another addon, surely not the only one.
I have the current C++ files, at least according to Microsoft.
"Current" VC++ libraries doesn't mean much. It's possible there's a problem with their installation, which is preventing the Side-by-side mechanism, which is supposed to allow two software programs using different versions of the libraries, to be loaded and executed at the same time, is not working correctly.
Actually, I don't think it is the KLAX scenery files, rather one of the scenery support programs/files.
It's not KLAX, and it's not the bglmanx.dll module. The module is the victim of a problem caused by a conflict, which can be either just a conflict with another FSX addon OR a problem of your VC++ libraries installation.
You cannot verify this, unless you turn off all your 3rd party modules *except* the FSDT ones, then test FSX in that situation. If it works and loads the module with no problems, you would KNOW the problem is a conflict with another module, so you only need to re-enable them ONE BY ONE, launch FSX every time, until you find the one causing the conflict.
If, instead, you still get the error even with NO other 3rd party modules enabled ( both in the DLL.XML file and in the EXE.XML file ) other than the FSDT ones, then you would KNOW the problem is, instead, a problem with your VC++ libraries, which are not correctly installed, or are just conflicting with themselves. Yes, there were issues when a version of the VC++ libraries caused issues with a different one.
So, the correct course of action, is not obviously "bail out" of KLAX, because this way you will NEVER find the REAL cause of the problem, but follow the above troubleshooting steps, which will give you a real indication of what the real cause is.
If you find this too difficult/complex, I'm always available for direct assistance with Teamviewer. PM me for details about it.