I did in the end implement my own add button which works well. The Prompt property of the AddNewBox style settings is for the text before the butto... Eg.

 <AddNewBox hidden="False" Prompt="Something random">
 </AddNewBox>

 would display the following:

Something random [ BUTTON TEXT ]

thanks heaps though for searching... 

 Here's how you change the prompt and Add New Button caption on the server side.  Put this code in the InitializeLayout method of the webgrid

     protected void myWebGrid_InitializeLayout(object sender, Infragistics.WebUI.UltraWebGrid.LayoutEventArgs e)
    {
        // Configure the Add new row of the uwg
        myWebGrid.DisplayLayout.AddNewBox.Hidden = false;
        myWebGrid.DisplayLayout.AllowAddNewDefault = Infragistics.WebUI.UltraWebGrid.AllowAddNew.Yes;
        myWebGrid.DisplayLayout.CellClickActionDefault = Infragistics.WebUI.UltraWebGrid.CellClickAction.Edit;
        myWebGrid.DisplayLayout.AllowUpdateDefault = Infragistics.WebUI.UltraWebGrid.AllowUpdate.Yes;
        myWebGrid.DisplayLayout.Bands[0].AddButtonCaption = "Add New Button Text goes here";
        myWebGrid.DisplayLayout.AddNewBox.Prompt = "Prompt goes here";

    }
 

I already had, I just posted something here as well since this is the only thread I found in the forums where people were talking about the Add Row button.

I believe it is best to ask directly in the Grid for WinForms forums here - chances are, you will get faster reply there.

http://forums.infragistics.com/forums/65.aspx 

Anyone have any idea how to do the same thing for a WinGrid?

 brilliant Amy! thanks!