Is the error not relating to 3D Secure Authentication?
We've tried a test with a Visa card and it works just fine (because Visa's don't require 3D Secure Authentication) which suggests that there is no problem with our start month format.
When you say you could help with the hand coding, does that mean you pretty much do it for us bar the actual dropping it into the page/s required?
Also, I've noticed that in a test order the "TruePrice" value, required because our unit price has incremental values added to it, isn't being saved to the OrderDetails table, just the regular unit price. Do I need to change a binding there? Which page is that?