Hi again,
Sorry for delay in replying. This is a SharePoint permissions thing. To save the form, they must have Edit permissions. This is actually a big issue, since users can easily delete forms on SharePoint. One partial solution is to remove the filename column from your default view so that they can't click the dropdown and edit/delete the form. This might help, but to truly lock it down, you'll want to use e-mail submission to a "gatekeeper" who uploads the form, or create an event handler in SharePoint that copies the forms to a special library, or submit to a Web service that has permissions to save the form (but disable the edit/delete from the form library). There are lots of options. Hopefully this gives you some ideas.
Patrick Halstead
Project Manager at Qdabra