CreateRectRgn doesn't work on printer device

[Paul R]

CreateRectRgn works fine with the default map mode (MM_TEXT) when drawing to a printer device, but when I use a different mode, such as MM_LOENGLISH or MM_ISOTROPIC it won't allow drawing inside or outside of the region. All the other GDI functions seem to work fine. CreateRectRgn or CreateRectRgnIndirect both return valid region handles, but when I select them I cannot draw anywhere on the printer device.
Maybe I am missing something really basic, but I would appreciate any help.