Changed IP, now remote site unavailable.

We recently had DSL installed after years of shared 56K dial-up to the internet. With the DSL came a change in IP addresses, due to a different ISP.

Our small ethernet network is connected to our even smaller remote office by a 56K leased line connected to Comsphere 3510 DSUs and Cisco 1005 routers. Changing IPs on routers to meet new network standards seemed OK but now DSUs show no line signal (there is a signal say phone companies that service us.

What gives?