I had the same issue on 4.x I think.
When using the Network Browser it shows the available computers on the network.
However when you select any specific computer (on the network) to reveal its shares the browser immediately returns to the first screen with no shares shown.
(that after the username / password dialog (I have none set))
I can mount the receiver's shares from Windows with no issues.
Also I can mount CIFS shares on the receiver by entering IPs directly.
All packages on the receiver have been updated.
Thanks for the help