Environment Material Disappears after ingame level restart

Hi, I'm kind of a newbie so this might sound a bit silly. While working on the survival shooting game tutorial I encountered a problem when restarting the level after the player dies:

 public void RestartLevel ()
     {
         Application.LoadLevel (Application.loadedLevel);
     }

(I call this function using an animator event). After restarting the scene, during the running of the game, the shadows just turn darker however after I exit the testing mode the entire environment loses its material and displays itself all just in plain white!

Note that only the environment is effected and not the characters, so I guess the problem is somehow connected to the environment renderer. thanx.