Sorry for cross posting from grass-user but maybe here there are more “vector gurus” 
I haven’t been able to find an explanation to the meaning of the square boxes that appear around my lines layer’s nodes, when I display topological informations on the map.
http://img543.imageshack.us/img543/8425/maptopo.png
I thought they could indicate errors, but my layer appear to be topologically ok.
Generally only labels are displayed for nodes. This is the only layer, between those I’m working on, that shows the boxes.
giovanni