Broadband connection problem

Just started using broadband at home. Using USB modem I have no problems. However I bought a D-Link 300T modem/router to share the connection with others at home via a switch. The switch also connects me to my work network via a bridge.
The d-link has been given a static IP address in the same subnet as my work.
When I disconnect the bridge I can surf the net but when the bridge is reconnected, the surfing stops.
The only difference I can see in the log of the modem is one line has been added:-
default route ioctl(SIOCADDRT): Network is unreachable
Computers are running XP Pro (pre SP2)
Anyone any ideas what this means?