I am running windows 7 32 bit with Foxit 5.1 and it does save. The problem may be something in Adobe.
That is one of the reasons I use Foxit, too. It can save form fillable PDFs even if the original PDF was not set to allow that functionality.
I went through the form fillable English sheets, but not the French or Spanish ones.
One of them is savable:
The other 3 are not: