VS 2010 Phantom Nodes In A Treeview?

I have a treeview that is populated with a hierarchical list of regions and locations. Each region has its own list of regions and locations - you can think of these as analogous to a folder structure in windows (ie a region is like a folder than can have subfolders and files within it).My code to populate the structure is called only once (I've put in breakpoints and stepped through the code), however my treeview shows two sets of the data. When I query how many nodes there are at the top level of the treeview it tells me there is only one node, but clearly there are two. If I delete the node at position 0 in the list of nodes one copy of the tree disappears but one still remains and it this point the count of nodes in the treeview is reported as zero.

I have a toolbar associated with the treeview which includes buttons to expand all and collapse all using the built in methods of the treeview (expandall and collapseall), and these only act on the first set of nodes and ignore the second set even though I can manually expand and collapse them at run time.I have code in the AfterSelect event of the treeview and this does fire for even the phantom nodes.The other odd thing is that the code to populate the tree assigns a key to each node, and so I would expect the code to fail if it was creating duplicate nodes as it would have duplicate keys