you have to realize it is not about your or your ineptitude. I am sure what you are sending them each time is just fine. it is just not their vision. this is about them not clearly communicating to you what they want so that you can create it for them. so they are failing not you. see if you cant find creative ways to question them so that you can get clearer ideas of what they want, when you finally get their approval, figure out what it was that made it finally click for you. the more you work with clients the easier it will become to ferret out what they want from the beginning. take care.