FSX automatically mistrusts modules (FSUIPC not loaded) - solution

I recently experienced a new (at least to me) FSX issue which Pete has asked me to document here. The problem was found when an updated version of FSUIPC wouldn't load into FSX even though the older one was loading fine, however the problem is actually generic and could affect any module.

There is a Windows registry setting which will result in FSX automatically mistrusting new (or updated) DLLs, without prompting. If you have a DLL that just will not load, and you do not even get prompted whether to trust it or not during FSX startup, you may be experiencing this problem.

If HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\WinTrust\State is set to a value of 0x63c00 then FSX will exhibit this behaviour. New DLLs (or updated modules) will automatically get added to the [TRUSTED] fsx.cfg with a suffix that indicates that they are untrusted and should not be loaded.

In fsx.cfg, a line like:

        S:\fsx\Modules\FSUIPC4.dll.rooctoroqihwhtikitinolctiqihrnaqeqkbqcor=1

is the normal format to indicate a trusted module. Sometimes, the value at the end of the line is a 2 instead of a 1, I am unsure exactly when a 2 is appropriate rather than a 1, but it seems to be something to do with a 2 being associated with modules that are part of an aircraft.

Mistrusted modules (modules marked not to be loaded) are indicates by a negative suffix, like:

        S:\fsx\Modules\FSUIPC4.dll.rooctoroqihwhtikitinolctiqihrnaqeqkbqcor=-1

The value at the end of the line could also be a -2.

If you were to edit fsx.cfg, and invert these negative suffixes (just remove the minus sign) then your new or updated module would load correctly on the next start of FSX. Of course, this would just be a workaround, and would not restore the normal behaviour of FSX asking whether to trust unseen modules or not.

The original MSDN documentation page relating to the possible values of HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\WinTrust\State and their meanings seems to no longer be available, however the default value is 0x23c00 and if you set State back to this value, the normal fsx prompting for trust behaviour will be restored. I am unsure what changed this value in my registry, but I suspect a piece of security software may be responsible.

[Originally posted in old support forums FAQ by user BorisTheSpider]