SOLVED: Required was unpublished in shopper fields - agreed. In 2.0.0-RC-2K this didn't stop it showing on the cart page, but in 2.0.0-RC-2L & 2.0.0-RC-2M it does.
The Terms of Service check box dissapeared with upgrade 2.0.0-RC-2L (from 2.0.0-RC-2K) on the cart page. Shoppers can't checkout with out agreeing to the terms of service so they can't get past this point.
Note: In Admin/Configuration/Checkout
Must agree to Terms of Service on EVERY ORDER? Off
Show Terms of Service on the cart/checkout? On
Changing the above options makes no difference - still can't checkout
Joomla Version 1.7.2
FYI: Problem still exists with upgrade to 2.0.0-RC-2M