NEW YORK (AP) - It's not me, it's you: Though it can be painful, sometimes, a business owner needs to break up with a customer.When Gil Gildner's big client started paying more slowly and stopped communicating well, cash flow was at stake."The payments became a week late, two weeks, a month late and then the final month it never came," says Gildner, co-founder of Discosloth, a marketing company in Little Rock, Arkansas.