I have a Similar problem, i have the latest version of P3D v2.5.12945.0, but unlike MPilotD i didn't have any errors during installation, but P3d doesn't start, i click on it and it closes about 5-10 seconds later, but when i don't have GSX on it doesn't close when i open P3d. (i know this because i was flying this morning, and didn't install any other addons, and i uninstalled GSX and it opened, and installed it again with no errors and it didn't open)
Now i'm not a big computer genius so i don't get whats being said in the link posted about re-saving in ANSI format... if that's even the fix to my problems
thanks in advance