Are you running Far Cry 3 within Steam? If so, try it directly from the .exe (the game folder will be in C:\Program Files\Steam\SteamApps by default) and see if the problem occurs. If it does, uninstall and reinstall the game. If it doesn't, use Steam to verify the integrity of the game's files (Library > right-click the game > Properties > Local Files tab) and see if the problem occurs.
If you still have the same problem, look at the Application log in Event Viewer (Control Panel > Administrative Tools). There will be a report which may give you further clues as to why the crash occurred. You can use this to search the Ubisoft forums or log a ticket with their support team.