I recovered my original dll.xml.
Your original DLL.XML was wrong, the only entry that was supposed to be there, was FSUIPC. In fact, I wonder how it's possible you won't get any errors from FSX.
Again, if GSX doesn't modify the XML files, the only possible explanation is that your registry entry for FSX is still wrong, as I've already explained in my first reply. Please check again your registry keys, and note there are TWO of them, one under HKEY_CURRENT_USER and one under HKEY_LOCAL_MACHINE.
As I've said, the correct one to use on a Windows version more recent than XP, is the one under HKEY_CURRENT_USER, and that's what our installer use to find FSX. If that one is wrong, but other add-ons are using the legacy key instead, you would be mislead thinking there's a problem with our installer, when it's just the fact you have the proper registry key wrong, and the legacy one correct.