support with credit card Machine

First, this probably isnt the right area to post this. Sorry, but im desperate. You guys seem to be good with with computer related equipment. We have a credit card processing unit and everything was working perfect until we went from roadrunner cable to DSL. Our credit card machine now will NOT connect through ethernet..only dial up. We have checked our router that it is plugged into and the port is lit so we know its connected. All of our laptops connect to the web all day long without problems .Anyone have any suggestions!?!? Thanks in advance!