Most likely this issue will be resolved if you re-open the add to cart server behavior and make sure the column settings are all set properly and then click ok so the code is updated.
Ray - further to my last message. I don't quite understand where I should be looking to update the add to cart server behaviour and how I would specify the value for the new column.
I added a column to the shipping called 'excess' for items that were heavy. I wanted it to pick up if I put a '1' in the 'excess' field in the add to cart. This seemed to be working ok but then I went in and changed the amount to charge for the excess and this happened. It not only happened on one page but on every page so now nobody can purchase from the site as it goes to the error message. I've hit a bit of a brick wall and can't get my head round what I should be doing to rectify the matter. Don't know if the attached helps