Hello Geoff

Thanks for your post.
It looks like a bug. The ColumnChooser remember the last location the used put it. So if it comes up on the wrong monitor and they move it to the current monitor, it will henceforth display where they moved it for the life of the application. But the initial display doesn’t take the location of the owning form into account.

I will log this issue to our development department and continue to follow as the support case. Please kindly take care of our notice.
In the meantime, you can work around it like so:

        private void UltraGrid1_BeforeColumnChooserDisplayed(object sender, BeforeColumnChooserDisplayedEventArgs e)
        {
            var screen = Infragistics.Win.Utilities.ScreenFromRectangle(this.Bounds);
            if (!screen.Bounds.Contains(e.Dialog.Bounds))
            {
                e.Dialog.Shown += Dialog_Shown;
            }
        }

        private void Dialog_Shown(object sender, EventArgs e)
        {
            var dialog = (Form)sender;
            dialog.Shown -= Dialog_Shown;
            var screen = Infragistics.Win.Utilities.ScreenFromRectangle(this.Bounds);
            dialog.DesktopBounds = new Rectangle(
                 screen.Bounds.X,
                 screen.Bounds.Y,
                 dialog.Bounds.Width,
                 dialog.Bounds.Height
                 );
        }

Sincerely,
Motoki.