Finally I got it. That is software only for experts.
No, it's not. It just that FSX has a bug that sometimes, a newly trusted module fails for no reason. The module obviously work, because once you get rid of that message (the Windows reboot usually fixes it), the *same* module ( because it hasn't obviously changed after a reboot ) that FSX mistakenly flagged as problematic, works and will never give that message again.
It's an FSX bug: the FS9 version use the same module, but it doens't have any of these issues.