That helped me fix my issue.

In the WebTree's InitializeTree clientside event I just set the scrollbar left property to 0 like this

function treeTPs_InitializeTree(treeId)
    {
        // this code will readjust the horizontal scrollbar
        // to fix the scroll bug
        igtree_getTreeById(treeId).Element.scrollLeft = 0;
    }

For future reference, I had to put this code in our clientside script to fix a bug I was having with the WebTree.  When the first node in the tree's display text goes off the screen and the tree renders the horizontal and verticle scrollbars it automatically adjusts the horizontal scrollbar which ends up scrolling the node expansion indicators (+ or - ) off the screen.  I tried toggling different properties but couldn't get it to stop auto adjusting the scrollbar.  This code resets it back.  Thanks again. 

Try the following:

igtree_getTreeById("UltraWebTree1").Element.scrollTop+=20;

This should scroll the tree by 20 pixels at a time.