Attached are some screenshots of Taxiway A at KDFW taken yesterday afternoon after two reinstalls of KDFW and the Stand Alone Manager from yesterday afternoon downloads from the FSDT website. So nothing is old or out of date. The internet connection has worked since last Thursday. I am using MS Security Essentials and Turning off the Windows Firewall during download and installation. All FSDT airports with the exception of KDFW are working.
I'm sorry, but the screenshot clearly shows your Addon Manager is an old version, the current version it's 2.9.0.1.
Since it's not possible to get an old version if the internet connection is working, the only possible explanation is that your internet connection is not working OR something is blocking the download, either the antivirus (but MS one is known not to cause this) or something else, like a firewall or an anti spyware, or even another antivirus still active, it wouldn't be the first time we had users with two antivirus installed without realizing it, usually because an old one wasn't uninstalled properly.
Fact you downloaded KDFW today doesn't change anything, it should have worked even with a previous version, the KDFW installer might not *contain* the most current version of the Addon Manager, but this is irrelevant, because the version contained in the installer won't be used if an internet connection is working.
However, if some external program (like a firewall) is blocking the download, the older one used in the installer will be used. And, if an antivirus is blocking it, you might THINK the download worked, because you would see files downloading, but then they will be blocked before being copied in the FSX folder, so you are stuck with the old version.
Since you ARE using an old version, that's the only possible explanation.
No, the KDFW installer is not "corrupt", if the installer was corrupt, it won't even launch (it obviously has self-integrity checks) and if it's was "wrong" it would't work for anyone, not just you.
As I've said, many times already, the problem is clearly in your system, and it's clearly something that is preventing the download of the current version of the Addon Manager.
In any case, as explained in many other threads on the forum, if you download and install the CURRENT version of Stand-Alone Addon Addon Manager for FSX and install it AFTER all the sceneries has being installed, it might work better, because it always contains the SAME version as the one that is online now so, it should work even if your internet connection is not working, or if some other product in your system is blocking the update.