Network established but can't see anything

I had a network setup between my PC and laptop successfulyy until I put in a
new motherboard (with integrated LAN) into the PC. Now when I run the setup
wizard I get a connection, the icons in the system tray show a connection
and I can surf the net from the laptop through the PC. I can't however see
anything from one computer to the other, nothing in network places, nothing
found on "search for computer". Shared files not visible. View workgroup
computers gives message "Mshome is not accessible. You might not have
permission to use this network resource. Contact the administrator of this
server to find out if you have access permissions. The list of servers for
this workgroup is not currently available."
Search for computer name - "no results to display"
I have run the wizard loads of times and it sets up a bridge betwen the 1394
and LAN connections, the bridge properties show TCP/IP correctly.
I have even put the NIC card from the previous setup on the new board but no
joy.
Can anyone give me a clue?