Verify Game Cache Steam Mac

So, I'm one of those unfortunate enough to suffer from crashes every 5 minutes, making Far Cry 3 unplayable: http://forums.ubi.com/showthread.php...-Bugs-Try-This
Browsing the internet looking for possible fixes, I read that one way was to verify your game cache through Steam.
However, when I tried this, it showed an error message at the end saying '1 files failed to validate and will be reacquired', and it then proceeded to download a 1.3KB file.
When I validated again, it showed the exact same message and downloaded the same file. I also closed Steam and reopened it, but the same thing happened when I tried to verify.
My other Steam games check out completely fine when I try this.
What does this mean? That I have to re-download FC3?
Verify Game Cache Steam Mac

Verify Game Cache Steam

CacheHow

Game Cache File

In order to verify your game cache, go to your 'Library' and find 'Dota 2'. Once you find it, 'Right Click' and go to the 'Properties ' tab. This will open up the properties tab. Go to the third sub-tab that says 'Local Files' where you will be presented with the following options. From the Library section, right-click on the game and select Properties from the menu. Select the Local files tab and click the ‘VERIFY INTEGRITY OF GAME CACHE’ button.