Funnily enough, I am on FF 3.0.3 under Win32!! The "Save Target As" issue is really a matter of my context menu being in Italian and me wanting to write it in a reasonably international way: I thought that the entry would be called "Save Destination As" but it is really "Salva destinazione con nome" for me.
I cannot exactly confirm Anonymonk's analysis, but indeed the behaviour seems not to be well defined: I tried several times on several different nodes now, and as you say, it works! But I'm sure I have not dreamt of it wanting it to save it to [download].htm yesterday and many other times in the past. Mystery?