What patch level of SAPgui are you running?
My guess is that the SAPgui is trying to render the default flavour but it just doesn't support enough of Personas to render anything. Try turning off Personas in SAPgui - Deactivating SAP Screen Personas - to see what happens. It might be that you need a newer patch level (6 is the newest currently, I think) or even need to wait a while for more complete Personas support in SAPgui.
Steve.