This has been explained many times already: you can safely ignore that warning: it's an FSX bug that happens sometime when the modules config changes and newly trusted modules are added.
It's not relevant to bglmanx.dll specifically: I get this error randomly for each and every FSX 3rd party module, sometimes it's lvld.dll, sometimes it's wilco.dll, but there's no pattern: the only pattern is that it sometimes happens after a new module is installed, or after an previsously installed module has been removed.
This can be usually fixed as follows:
- Edit your %APPDATA%\microsoft\FSX\FSX.CFG with a text editor. Find ALL the occurences of the bglmanx.dll and couatl.exe files in the [Trusted] section, and remove the whole line that contains either reference to those files. This will reset the trusting question.
- Reboot Windows (IMPORTANT). Don't launch FSX yet.
- Uninstall ANY scenery (or the stand-alone Addon Manager), and (IMPORTANT) reply YES to BOTH questions about removing the Addon Manager AND the Couatl engine. Reply YES to BOTH question. This is important, and it will remove all files.
- To be sure, check you don't have any bglmanx* (.dll and .dat files) in your FSX root, and you don't have the fsdreamteam\Couatl.exe. If you still have them, remove them manually.
- Reinstall the scenery you just uninstalled (or the stand-alone Addon Manager, if this is what you uninstalled in the previous step)
- Launch FSX, and note it should ask you permission to run BOTH the Addon Manager and the Couatl Scripting Engine. Reply YES to both, and reply YES to both the question made by Windows (yellow Shield) AND the question made by FSX. If you are not getting both questions, it means you haven't properly cleared the [Trusted] section in the FSX.CFG as above.
- If you get any error, disregard the fact that is suggesting not to run the module, and ALLOW the module to run. It doens't matter if the FSX crashes now.
- Try again to launch FSX, and see if it works. If still crashes, reboot Window AGAIN (IMPORTANT), and try again.