Then I delete my FSX.CFG file so FSX could rebuild a new one. Now everything is working perfectly.
This clearly proves the problem never had ANYTHING to do with GSX, FSDT in the first place. What *likely* happened, is that your previous FSX.CFG was corrupted by OTHER defective addon installers, or by having edited it by hand.
Specifically, it was surely an issue with the default lines that contains the SimobjectsPaths: we install our our objects in the Simobjects\Misc folder, which
is included in every default FSX installation but, if the lines that references it in the FSX.CFG is missing/corrupted, the sim wouldn't be able to find the objects, so nothing will work.
You'll lose also hundreds of default library objects used by sceneries too but, of course, you might not noticed them if you don't fly on default airports much.
More detailed information about this here:
http://www.fsdreamteam.com/forum/index.php/topic,14184.msg104782.html#msg104782The issue is, we can test for the file being there (in fact, we do), but if the FSX.CFG line is missing, the sim will cause an error nonetheless, even if the files are there. And of course, you won't still see the objects so, nothing will work just the same.
We considered testing the SimobjectPaths being correct with the installer, as we test several things that could be messed by other defective installers from other products (like the DLL/EXE XML files) but the issue is, if the file contains errors, like illegal comments, messed up lines, it would be VERY easy to damage irreparably if we tried to touch it. At least, to report a problem with an XML file, we can rely on the default XML parsing routine that comes with Windows but still, we only REPORT errors, but don't try to fix them, because it will be extremely dangerous, on an already-corrupted file.
The issue with FSX, is that too many files are centralized so, if one defective installer (or hand-edit the file) is messing up with it, it might affect other product which are UNFAIRLY taking the blame, like GSX in this case.
At least, Prepar3D has a new way of install addons that would allow using localized folders (each addon can have its own XML files, for example), so we can only try to use these feature in later version of our installers, in order not to have users being MISLEAD into thinking the problem they are having are in any way related to our products. For the FSX, you just have to pay more attention to your config files.