Camera Bug World Editor

Hi everyone, i'm getting a bug (maybe) with the camera inside the world editor... when i go inside it i usually move cars etc... nothing strange i just pick up them and move, often when i try to move them the camera moves a lot and very fast (i don't press any button to move it) i just take the 3 arrows to move the car and olso the camera does this. This problem makes the world editor impossible to use....someone can help me? Sorry for bad english but i'm italian.

 

the only way i have found that fixes this is to hit "shift+c" and that will put in free camera.