When I try to launch games it tries "validating" the files.
It says it gets to 100% but then it doesn't launch the game.
To validate a game’s cache, right-click the game in your Steam library and select Properties.
In the properties window, click the Local Files tab and click the Verify Integrity of Game Cache button.
I've tried completely uninstalling and reinstalling the offending game to no avail.
I've also run the Disk Checking tools from my C Drive Properties Tools menu, as well as run "chkdsk /f" which runs chkdsk on boot, neither run showed any errors in the drive.
To fix corrupted game files, you can have Steam validate the game’s cache on your system.
Steam will examine the game’s files and – if any problems are detected – will re-download the corrupted files from Steam’s servers.
It has happened on two games now: Total War Rome II and Call of Duty Ghosts.
Is there any way to back up Steam games without waiting forever to download them again? Steam packs a lot of useful features into its client software, including game backups, although you can always do it yourself once you know where Valve buries the bodies during installation.
Official client backups begin on the Steam menu via the library view.
I'm definitely keeping in mind my recent comment that if you look at Steam more as a "software as a service/MMO" type model it's easier to have "serenity now" about these hiccups.
:) No idea if it's related, but recently when trying to launch HL2 it would occasionally open the main Steam window instead of launching the game.