NEVER happened to me. I've bought over 10 domains at DynaDot, and each time, the transaction was instant. It's possible that your PayPal account is flagged as suspicious, and it is PayPal that is holding up your transactions.
That's just a sacrifice you have to make for the privilege of shopping in your underwear. Once you've been with PayPal for a couple months/years, and you've made a few transactions, you'll have to go through less verification stages when making a purchase.
I'm so sorry you are having problems. I just registered my first domain with this company a few minutes ago (after hearing from friends and reading many, many sites on recommendations), and mine is immediately showing up as taken. It IS frustrating when things go wrong, but perhaps you should call them and figure out the problem. They are great on the phone and I'm sure can help you.