Thanks guys,
I was thinking of the same thing.
But the weird part is, I was not passing any ship method and the eConnect's programming guide mentions that the ship method is not mandatory and it inherits from the customer number. Also, we starting getting the errors starting yesterday and the process has been in place for atleast 2 years now. We never had any issue with it. This is what is bugging me. Any ideas ?
Thanks again for the help.