If you do not use New in REALbasic.Rect, the application will be build and crash, if you run the code where REALabsic.Rect appears.
Not sure at 100% it does the same on r2.1 and r3.
Windows 8.1
Dim myBounds As Realbasic.Rect
myBounds.Left = 100 // Compiles, but crash here when that code runs
myBounds.Top = 100
Self.Bounds = myBounds
Example code comes from WIndow.Bounds AND I REMOVED NEW from the first line.