Ubuntu (samba) not visible from Windows 7

On my home network there's an ubuntu machine that shares printers using samba. I have windows xp, vista and win 7 machines that can happily print (these are all running another security product).

 

We have just bought a laptop with Norton installed and I think it might be preventing access to these printers. I have first tried manipulating windows and network settings to no avail.

 

The ubuntu machine is not visible on the Network Security Map, although it does show up in windows explorer under Network. All other devices on the network (inc routers and smartphones that don't show in windows) do appear on the map.

 

On the other windows machines, I could add the printers either by browsing in explorer or failing that, typing the names in directly, without using any credentials. On the new laptop, I get a windows network security error that asks for username and password, and none of the possible combinations have worked.

 

I tried adding a device to the Network Security Map (it appeared in Trust Control instead of the network), giving it the same device name and IP address and making it fully trusted but this made no difference so I removed it again.

 

Is there something that needs changing to make the ubuntu/samba machine appear in the map? It appears on the map of the other security product running on the other windows machines. Or is the map irrelevant and there's something else I need to change? I can ping the machine both by ip and name.

 

Thanks in advance.