I have an issue where the contents and scrollbars overflow the pop-up window regardless of its height. It only overflows a couple of px, but its enough to be annoying. I attached a small image of what the window looks like.
Try the following CSS in your page, it fixes the issue on my side (it will not remove the vertical scroll of the form itself, it is applied to its parent element).
<style type="text/css">
.RadGrid_SkinName .rgEditForm
{
overflow:hidden;
}
</style>
(replace SkinName with the name of the skin used by the grid)