Is there a deconstruct button? If there isn't there should be. Every now and then I trap myself in between barriers and turrets and it gets frustrating after a while.
Your game seems awfully similar to this one featured in this tutorial commonly found around the internet...are you by any chance the author?
http://www.gamesheep.com/free/flash-tutorials/1-flash-racing-game-1/flash-tutorial-1-4.php