Similar issue, I cannot get 'next' buttom to go to payment screens on 2.6.9. I tried to go to 2.7.0h but all my fields - custom or otherwise, vanished, and now I can't get to the next (payment) screen on 2.6.9 either. I'm tempted to roll back even further on this one (2.6.6 is the latest one I seem to have saved).
Please update to 2.7.0i and you should find this issue is resolved. Thanks!
Ann - you need to upgrade to the latest 2.7. If your fields aren't showing, then they are not assigned to your events properly. Upgrade then re-save each of your fields to make sure the default settings are as desired. Then open your events and make sure Field settings are what you want and re-save them.