Delete your old shortcuts if you have made any.
Go to Steam Library and go to your FarCry 3 game and "right click"
Go to properties
Go to tab "Local files"
Go to "Browse Local files"
Go to the "bin" folder.
Right click "farcry3_d3d11" executable.
Go to the "Capatabilites" tab.
Look for the privilege level at the bottom and select "Run this program as administrator"
NOW! not done. Cause just doing this last time didn't work and did nothing, with just selecting the first run as admin mode; but this extra step seem to work and now I can play like normal. Also launching from Steam and using a Steam Shortcut. Like normal. Like it should've been day one.
Don't close out your window yet. Right below the checking the "Run this program as administrator" Click on the tab that says "Change settings for all users" I don't know why this makes a difference I'm the only one that uses this computer. But it worked for me so it won't hurt to share this or try it whatever.
Now under that tab check "Run this program as administrator" at the bottom.
Now do this for the FC3UpdaterSteam exe and the DX9 exe or the normal FC3 exe.