I am building the top level on the server but the lowest levels are been populated by demand at cliente side using a javascript function that read data from json,  IE7 and IE9  works fine but in IE8 i am having a strange behavior the nodes are been added twice for each node, I am attaching a image of the bug and the code, please could you help me because there is not documentation that help me

We were using the event LoadByDemand of the tree, but was causing performance problems because delay and the viewstate weigth