Thanks for the reply. I am using telerik version 2011.02.915.35.
I create all the tree nodes from the code behind. and at the node expand event i add the child nodes. The problem is that after the node expand if I click any node, either top level or a child, the page will refresh. but if i don't expand any node than i can click on any node in first level and it works correctly.
I am attaching a video here http://screencast.com/t/jfOxLY3ouhbP
that should explain what i am saying. in the video i use the same code which is used as a module in 2 different DNN versions, 5.x and 6.x. Then it shows the same tree structure and the functionality in the module. In DNN 6 the node click event after expanding any node triggers a page refresh and this does not happen in the DNN 5.