Can't Access Other Computers On Windows 7 Network With Vonage And D-Link Router

I have 2 Windows 7 desktops that are both connected to seperate vonage boxes and those vonage boxes are connected to my D-Link DIR-655 router. That D-Link router is getting its connection from a Comcast router. I am looking to get one of the desktops to share a printer from the other one which has it hard wired via USB cable. When I first set this up I did not have the vonage boxes and the desktops were connected right into the router and everything worked fine. Now that the vonage boxes are in place it is a mess. I can get internet fine on both machines, but no file/printer sharing. I have followed all the steps to setup the correct workgroup and file and printer sharing options on both windows 7 machines but they cannot see each other at all. My feeling is that now that the vonage boxes are there that instead of the desktops looking at the D-Link router for its sharing option they are looking at the vonage boxes and that is why they cant be seen. Does this make sense? Is there a firewall on the vonage boxes stopping these two desktops from seeing each other? Do I have to change something on the D-Link router options for it to give access to the vonage boxes for these 2 machines to see each other for printer/file sharing?