I'm having the same problem. I tyook Georges advice but found no box for advanced animations. I have XP SP2 & FSX.
The Advanced Animations is surely there in the FSX Graphic settings, check better. Also, if you are looking from far away, there's a built-in FSX optimization that turns off all animation, you simply need to look from a closer distance.
Other things that might cause this problem, are video driver settings and wrong tweaks in your FS.CFG;
- First try to reset your video driver settings to default. Be sure you don't use "Transparency Antialiasing" (or "Adaptive Anti-aliasing" ).
- If that doesn't work, try to update your video driver too.
- If that doesn't work, try to reset your %APPDATA%\Microsoft\FSX\FSX.CFG file, to have FSX rebuild a new one with default settings
- Be sure you apply the HIGHMEMFIX tweak to the FSX.CFG, you can enabled it with the Addon Manager too, that's the only setting that really needs to be applied.