Did you try it with the IP address instead of the computer name? Usually when you get this type of network path not found error it means that either Netbios information is not working or is being blocked. Check the machine hosting the share that you can't get to for firewall settings, if you have any third party firewalls on that machine or third party antivirus / internet security suites, temporarily uninstall them so you can determine if there causing the problem. You can always reinstall them later. Also you can temporarily turn off the windows firewall and see if that's blocking your sharing.