Not sure if this has been posted here already, but it seems that recent Win10 Redstone 3 builds (internal name for the next big Win10 update, due to be released in Fall 2017) are rendering 3rd party addons unusable due to changes in OneCore which is an essential part of Win10 (its part of the "Windows Everywhere" strategy allowing all Microsoft hardware platforms to use the same OS core, Desktop, Mobile and Xbox). This seems to affect pop up window handling of 3rd party addons for P3D/FSX.
AFAIK. Redstone3 is currently only being rolled out to fast ring insider members but it might soon be extended to slow ring participants. Its currently unclear if those issues are due to a bug or an intentional change within OneCore. If its the latter then brace yourself as this would mean that many addons will require an update once the new Win10 build will be rolled out to end users.
So if your sim recently started to act funny, ranging from "error creating child window", CTDs after loading scenario (PMDG 747), chaseplane and ezdok no longer working, erratic behavior of FSLabs A320 and being unable to open any add on windows like FSUIPC, GSX and everything else that sits under the addon tab in P3D, then welcome to my world....you are likely a member of Win10 insider preview.
Looks like opting out of insider preview will require a complete reinstall of Win10, so i might sit this one out. I just hope its not going to be a permanent change that will require all addons with pop up windows to be updated.