Every time you reset the Trusted section, you need to reboot Windows. And try several times, because this problem usually fixes itself if you try it several times, and allow some time (like 20-30 secs) between each FSX launch. And, always ALLOW the module to run, even if FSX crashes.
If the registry value is ok (zeros do not count), don't touch it.
Also, try running FSX as Administrator (it shouldn't be necessarry, but it might be worth trying).