I have a bank account and debit card attached to my paypal account, and I can't add money to my account. The only way to add money is through ebay sale. So when I had two recent returns that had to refunded, nothing would budge until I added money through selling on ebay, once the negative balance got to zero they released the funds so they could be refunded.

When I sell something I pay to have the balance sent to my bank account instantly. So I leave zero balance in my account, when paypal gets a hint of return they charge my account the sum giving it a negative balance, holding it until I make good. Which is only by selling more on ebay. :(