If it doesn't run try this:

1.If another game is downloading, then it's a steam setting that doesn't allow a game to be run. (in Download settings)
2.Install manually from the game folder (C:\Program Files (x86)\Steam\steamapps\common\FlatOut Ultimate Carnage) the GamesForWindowsLive application (XLiveRedist01.02.0241.00) and it will run
3.If that doesn't work either , then install manually everything from the Support folder from the before mentioned path.
It works after any or all these steps!

If it doesn't run try this: 1.If another game is downloading, then it's a steam setting that doesn't allow a game to be run. (in Download settings) 2.Install manually from the game folder (C:\Program Files (x86)\Steam\steamapps\common\FlatOut Ultimate Carnage) the GamesForWindowsLive application (XLiveRedist01.02.0241.00) and it will run 3.If that doesn't work either , then install manually everything from the Support folder from the before mentioned path. It works after any or all these steps!