I resolved this issue myself but I thought I would post it so anyone else having the issue could solve it.

I was working on a project that uses Infragistics NetAdvantage 2007 vol 1 and I changed the toolbar to a Ribbon style. I did the same with some other MDI child forms, hoping the Ribbons would merge. They did merge, but every time I got an exception (posted below). In addition, the MDI child had a red border along the bottom, almost as if there was a Windows control down there that had the infamous "Red X" that shows up when a control has thrown an exception in its paint event.

The solution was upgrading to NetAdvantage 2008 vol 3 with the latest hotfixes.

Now back to coding. Infragistics NetAdvantage rocks :)

 System.NullReferenceException: Object reference not set to an instance of an object.
   at Infragistics.Win.UltraWinToolbars.UltraToolbarsDockAreaUIElement.PositionChildElements()
   at Infragistics.Win.UIElement.VerifyChildElements(ControlUIElementBase controlElement, Boolean recursive)
   at Infragistics.Win.UIElement.DrawHelper(Graphics graphics, Rectangle invalidRectangle, Boolean doubleBuffer, AlphaBlendMode alphaBlendMode, Boolean clipText, Boolean forceDrawAsFocused, Boolean preventAlphaBlendGraphics)
   at Infragistics.Win.ControlUIElementBase.Draw(Graphics graphics, Rectangle invalidRectangle, Boolean doubleBuffer, AlphaBlendMode alphaBlendMode, Size elementSize, Boolean preventAlphaBlendGraphics)
   at Infragistics.Win.ControlUIElementBase.Draw(Graphics graphics, Rectangle invalidRectangle, Boolean doubleBuffer, AlphaBlendMode alphaBlendMode)
   at Infragistics.Win.UltraControlBase.OnPaint(PaintEventArgs pe)
   at Infragistics.Win.UltraWinToolbars.UltraToolbarsDockArea.OnPaint(PaintEventArgs pe)
   at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer, Boolean disposeEventArgs)
   at System.Windows.Forms.Control.WmPaint(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)