This is a heads up for everyone. When Easy Digital Downloads v1.4.3 is released sometime tomorrow, we will be waving goodbye to the jQuery Validation option for checkout.
This was an option enabled in the Misc settings and added a nice layer of live field validation to the checkout screen. We have decided to remove it due to on-going compatibility issues with it an other systems, primarily certain payment gateways.
In version 1.4.2 we introduced a better, fully ajaxed checkout that more or less took the place of the jQuery Validation, though the jQuery Validation was still an option.
The primary reason for this notice is to alert anyone that may have created their own custom styling for error fields during checkout.
If there are any questions or concerns, ask in the comments.
Bravo, this is a move in the right direction.