cant save xbox 360 marvel ultimate alliance 2?...

Anyone know why I can't save my progress?...it gives me three options, save, load and quit and it won't let me save. I can't move up to the save option. I've tried at all sorts of places, at the secret base, during gameplay, but it won't let me save anywhere. I'm playing with my nephew and I'm getting in trouble because it's past his bedtime!

Also of note, if you use cheats... This game will not let you save at all.

Yeah I have the space on the hard drive, it's a 120gb drive and I only have about three game saves on it. And nope I don't use cheats. My nephew will be around again tomorrow so I can just leave it on till then or I could get him to throw a sickie!. Is it OK to leave the xbox on for a few days if no-one can help me get it saved?...thanks.

Crisis over, I yanked out the hard drive in order to check it was properly inserted and it first made me panic because it took me out of the game and back to the dashboard, then I started the game and everything was saved automatically anyway, NICE. thanks everyone.