restart your vista comp, also set up a samba password
also make sure guest account in vista is activated. If your using a firewall that's not windows firewall make sure the file sharing ports are open. Are you using a router, or a switch? if your using a switch make sure the 2 aren't using the same ip address. Networking is more complicating than most people think, and there are a hundred little things that could cause problems. If your using a router is the modem configured properly for the use of a router? If every networking issue could be addressed with point, and click we wouldn't have tens of thousands of network administrators.
sudo smbpasswd -a "user name"