I have a small home network both via LAN and wireless. On one computer MY NETWORK PLACES does not appear to function properly ie it does not see any shared folders on the other computers that are currently running. The only way it will work is by adding a network place using the wizard.
I had initial problems with my network. Like you I had one computer which could not see the shared folders on the other computer but the other computer could. I turned off my firewall software completely. Found the shared folders OK. Turned the firewall software back on and could still see the shared folder. I don't know why this works but have a go it may work for you.