Are you referring to the fact that clicking on the dropdown button of a ValueList will cause you to go into edit mode?  You could certainly prevent this by keeping a flag to cancel going into edit mode unless you are specifically the one putting the grid in edit mode, such as:

 private bool isEnteringEditMode;

private void ultraGrid1_DoubleClickCell(object sender, Infragistics.Win.UltraWinGrid.DoubleClickCellEventArgs e)
{
    try
    {
        this.isEnteringEditMode = true;
        e.Cell.Activate();
        this.ultraGrid1.PerformAction(Infragistics.Win.UltraWinGrid.UltraGridAction.EnterEditMode);
    }
    finally
    {
        this.isEnteringEditMode = false;
    }
}

private void ultraGrid1_BeforeEnterEditMode(object sender, CancelEventArgs e)
{
    e.Cancel = !this.isEnteringEditMode;
}

This may be unintuitive to the user, though, since the cell will still display the dropdown button, and the only built-in option that I can think of to control when the button will be displayed is the ButtonDisplayStyle of the column, which will show the button when the cell is activated.

-Matt