I've the same problem that this post (http://www.telerik.com/community/forums/silverlight/treelist/treelistview-crashes-with-more-than-8-items.aspx).
When I have more than 8 items, Drag&drop crashes on the "CumulativeValue" method in IndexTree class.
I think that this problem due to the constructor of IndexTree class :
When you drag an element, i think this element is temporary duplicated. So "size" property is smallest
is there a trick to solve this problem ?
.count = capacity;
.size = 8;
.size < capacity)
.size << 1;
.size << 1];
.itemDefaultValue = defaultValue;
Thanks to your help.