OK, SP2 won't solve this. The "locks" that you see is a Namespace issue because the schema was designed outside the InfoPath schema builder. Do you have the free Home version of XMLSpy on your machine (from Altova - great German company!)? Open your schema in XMLSpy, you should be able to modify names. But, be careful, if you change the name of a field used in UI logic, the name change won't be automatically reflected across the form.
Regards,
Franck Dauché