Please check the options below:

• Restart Steam and then check if the game runs
• Run Steam in administrator mode then launch the game
• Launch the game from the game's library
• Launch the game as an administrator
• Delete the game's reg keys at HKEY_CURRENT_USER\Software\NeoCore Games\Warhammer Martyr\ 

The last one reportedly helped a player 2 days ago who ran into the same problem.