viewing samba shares using Gnome-VFS and many other techniques has always been flakey. I would strongly suggest just mounting the share locally within a folder using CIFS and I gurantee you won't get the unable to open error. here's a guide for mounting windows shares with cifs:
http://ubuntuforums.org/showthread.php?t=288534
you don't need to install winbind and what not, you can always just use the IP address instead of the netbios name, if you can already ping the machine by hostname/netbios name, then you CAN use the netbios name when mounting with CIFS. good luck.
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