That's because either you or another addon has mistakenly set FSX to run into a Compatibility mode, like XP/Vista/Win7 under Windows 8 or similar, which is not how FSX is installed by default or should run.
First thing to check, is that you are NOT running FSX into any of the “Compatibility” modes, like XP or Vista Compatibility mode. To check this, go into your FSX main folder, look for the FSX.EXE file, right-click on it, select “Properties”; then select the “Compatibility” tab, and be sure NOTHING is enabled there. All checks should be off, which is how FSX is installed by default.
However, even if you don’t use Windows 8, the suggestion about turning off every “ Compatibility” mode, is valid under Windows 7 too.
Note that, this could happen also if you set ANOTHER add-on that starts together with FSX in Compatibility mode, so it should be turned off for it too.
