You are using InfoPath 2007 features - InfoPath detects it and marks views as not-designable in IP2003.
Normally Design Checker (Tools | Design Checker) should tell you what those features are but unfortunately not all features are listed. For example, dynamic text for buttons is not supported in IP2003 designer.
If you save your solution as source files and inspect manifest.xsf, you will notice that InfoPath puts the designMode="protected" attributes on the views that contain incompatible features. DO NOT REMOVE this attribute! Instead, try to play with your solution so that InfoPath removes this attribute by itself.
I hope it makes sense...
I would recommend not worring about IP2003 designer though, the new IP2007 features are worth it! :)
David Airapetyan / Software Services ArchitectQdabra® Software / Streamline data gathering to turn process into knowledge