Completely clueless with networking but somehow managed to get all four of my puters linked up ... until recently.

I've got one nettop and one laptop running ubuntu 12.04, one laptop running lm13 and one running windows.

I'm using the nettop as the 'server' for files etc. and all was working fine until recently.

When I'm running nautilus and I click in the 'Browse Network' link I get the window showing the WORKGROUP 'folder'.

When I click on WORKGROUP I get a dialogue which says:

You can stop this operation by clicking cancel

Then, after a little while, I get this:

Unable to mount location

Failed to retrieve share list from server

It seems that I may have done something in the last few days to stop it all working but I've no idea what ... can anyone help me resolve this?