I ran into this same very issue on a Xerox C70 and was able to resolve it using the following process.
1. I created an account on the server with a username and password.
2. I shared a folder on the server, for scans to come too.
3. I opened an incomming port 139 in windows firewall advanced features to allow the printer to communicate with the server.
4. In the network scan settings for the C70 I chose SMB as the protocool.
5. The host name is the ip address of the server.
6. The port is 139.
7. Shared name would be the name of the folder shared on step 2.
8. Selected System in the Login Authenication section.
9. Entered the details from the account you created in step 1.
10. Was able to succssfully scan to the networked location.
-I hope this helps.