Urgent: NullReferenceException on RenderControl method of TreeView

[LanceM]

I get a NullReferenceException on the RenderControl method of the new
Treeview web server control for ASP.NET version 2.0.

The exception message is: "Object reference not set to an instance of an
object."

The stack trace is: "at System.Web.UI.WebControls.TreeView.GetImageUrl(Int32
index)\r\n at System.Web.UI.WebControls.TreeNode.Render(HtmlTextWriter
writer, Int32 position, Boolean[] isLast, Boolean enabled)\r\n at
System.Web.UI.WebControls.TreeView.RenderContents(HtmlTextWriter writer)\r\n
at System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer)\r\n
at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer,
ControlAdapter adapter)\r\n at
System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter
adapter)\r\n at System.Web.UI.Control.RenderControl(HtmlTextWriter
writer)\r\n at
dmgTools.UserInterFace.Web_Controls.WebTabControl.RenderTabs() in
C:\\Projects\\Source\\Framework\\UserInterface\\Web
Controls\\WebTabControl\\WebTabControl.cs:line 310"

Other posts have suggested setting the SkipLinkText property of the Treeview
to "". I have done this but it doesn't help. I found that setting the
ShowExpandCollapse property to false lets me run the RenderControl method but
I need it to be true so I can navigate through the child nodes. I tried
setting the ExpandImageUrl and CollapseImageUrl properties and setting
ImageSet="custom" but this didn't help. I have run out of ideas. Can
someone please help (maybe someone from Microsoft)? This is really urgent.

Thanks,

Lance