Saving problems

I've been having an odd problem. It's happened twice now. Went away for a while then happened with my newest character. This is on Xbox.

I will be playing the game, when suddenly I get a message saying I'm out of memory space. I have 70 gigs left. I delete older saves for that character, and eventually I can only have a single save for the character. What's the deal with this? I have only have three characters. Well, 5 if mods count. But that shouldn't matter if my xbox has plenty of memory right?