Tree status lost after page refresh

Got a strange thing today - once page is refreshed, the tree state (opened nodes) is lost and displayed again with all nodes collapsed. But the node expansion arrows do show the correct state - "expanded"...

Take a look at thetwo screenshots - first one displays the tree after several nodes were expanded. Second - how the tree looks like after the browser page is refreshed - note, that arrow icons and node icons are displaying the correct state, however no expanded children are rendered.

If double-click the expanded arrow (to collaps and expand node again) everything is drawn correctly.

Could someone give me a glue where to dig ? Could it be an error in my implementation of hierarchial container (it is filesystem container based, just the hierarchy datasource changed - we pull data from the database)

(Vaadin 6.3 is used)

Thanks,
Dmitri

Never mind, I found the problem.

Yes, that was a container issue. I got my brains mixed up with the following two methods: hasChildren and areChildrenAllowed. One of them (hasChildren) was missed, always returning false :*)