pollyhoek

I started a new game on a borrowed 360 yesterday and it won't save at all. No autosaves, no hard saves, nothing. Evidently the 360 was saving Assassin's Creed just fine before I borrowed it for Bioshock. I've never actually owned a 360 so any input would be helpful. The hard drive says there's over 100 gigs of space left, so nobody seems to know what's going on.  Help?