On the Twin I can't get Network Browser connecting to anything on my network either. Must have something locked down too much.
This is how I set mine up using a Windows 7 machine on fixed IP.
On your PC setup your folder for sharing and give it a share name - keep it simple for now with no space eg. films
Then on box (assuming it's same as Twin)
Lan > MountManager > Add new network mount point
Mount using: FSTAB (mount using linux)
Active: enable
Local share name: twin-film (for example)
Mount type: CIFS share
Server IP: 192.168.0.2 (whatever your PC IP is)
Server share: /films (what you shared as on PC)
use as HDD replacement: no
Mount options: rw (or ro for read only)
Username: boris (account name on PC with share rights)
Password: blah (account names password)
Press OK and hopefully you'll get some positive response
You can then check on whether each mount has a tick or cross next to it showing whether it's working properly by going back a level and selecting Mountpoints management