that's not an error - everything looks like it's being loaded properly:
ASI loaded : C:\Program Files\Rockstar Games\Grand Theft Auto IV\Car Bomb.asi, Address 0x03990000
^ that means it's loading ^
Tell me, how are you testing it? Are you just pressing Start to begin your game and then you walk behind a car and press F3? The reason I ask is because the script will not work if you load one game and then start another. It will only work the first time you load a game.