I CAN'T 'Proceed to Checkout'

When I'm in my cart and ready to purchase, I click 'Proceed to Checkout' but NOTHING happens. It just thinks and thinks and if it does anything, it just sends a message that it's having 'technical difficulties'. Well, I've been trying to checkout for 4 hours and it's gettng really frustrating. I've never had this issue before. PLEASE fix this problem! Thank you.