Hi Michelle,
Are the users filling the form with Adobe Reader? If yes then the form must have Extended Adobe Reader Rights applied to it to allow filling and saving in Reader. If you have Acrobat 8 Pro, 9 Pro or Standard or later you apply the Rights under the Advanced tab in Acrobat ( the wording has changed between versions but the menu item says something like Extend Rights or Enable Rights....). In Acrobat X, you apply the Rights by going to Save-As and selecting it from there.
Hope this helps,
Dimitri
WindJack Solutions
www.pdfscripting.com
www.windjack.com