Problem with Https and Treeview control

[Steve]

If we set our web site up normally (i.e. using http), then the treeview we
use on some of our pages works fine.

If we put RSA security on (https) both our web site and the web controls
virtual directory, we get the error message : "The XML loaded from
TreeNodeSrc=.\stylesheet\dotnet\TreeViewStyles.xml, TreeNodeXslSrc= did not
contain the required outer <TREENODES> container".

Does anyone have any ideas why this happens or what sort of things I should
look at ?

TIA

Steve