Since you did not answer any of the posting tips, this is possibly more informational than helpful. I have no idea if you are using OPC, a template that might be a problem, or some other situation.

A generic decline means that some information was not entered or entered incorrectly. Since the billing address/zip is an important part of the transaction verificaton, payment gateways will never specify to the customer what was "generically" incorrect. It gives information that bad guys can use to get information not found on hte card. Since the newest WebPay is set to not allow checking out without filling the form with all the info, my money's on the information being incorrect.

One problem that comes up in Chrome and other browsers is that it may be set to automatically fill in the shipping/billing and has a tendency to add the city into the Address 2 block. That will cause a generic decline. Another instance is a user with a corporate CC using their home zip instead of that for the card's billing address. Both situations result in a generic decline.

Review every entry on the checkout page