Network places/entire windows network not visible

Opus 10.2.0.0, XP SP3 up to date. I used to be able to drill down through Entire Windows Network to my home office network (3 PCs, router, drives etc), but recently (not sure how recently) I get as far as the name of the network then just a blank window (tree in the pane on the left as usual) with just the network name in it and nothing else. Double clicking sends it off for a few seconds, then the same comes back.

I've tried playing with the firewall (Zone Alarm), no different.

Network settings have not been changed, file and print sharing enabled.

Grateful for any help.

What does Windows Explorer show?

Hah, Windows Explorer has the same disease, so presumably I must go off to find a windows networking forum. I've spent much of today chasing this, without success...
All the settings on networking seem to be correct, at one stage I got an Error 6118 message, but was not very successful in finding anything helpful on this.