I was having this same issue, but no longer. I can think of two reason you might be having this issue:
1) 2.1.0 had a few bugs and could have been responsible for this... after installing 2.1.1 I saw a number of issues go away.
2) Look at your payment configuration and try isolating the problem. For instance, try to enable only "Check or Money Order" and see if you get to the payment page. If so, it could be an issue with the payment method configuration. For instance, I have Authorize.Net Direct Post set to "Test Mode", and I'd get what looked like an error and the payment page would never finish loading... but after taking it out of "Test Mode" and testing with a small "Authorize Only" order, all works as expected.