Yep, me too. Which is why it's cash upfront (50%) for me now. I wouldn't take on DJ work without a retainer, graphic design is no different. Another change to the way I work is I no longer provide a large batch of different samples and concepts. I only take on a design if there is enough information to get a good grasp of what people are after, I'll then provide the one design based on their exact requirements. I don't mind making alterations to get it just right, but I won't mess around with half a dozen different design concepts per client anymore. I much prefer working to someones specific requirements than having to second guess what they may be after. I think this was the main reason I enjoyed doing Tom (goodknight DJ's) logo....he knew exactly the look he was after, which made the project a lot more fun.
Since I changed the way I do things I've been busier than ever and I'm enjoying it a lot more.