Has anyone else had a problem saving mid-level?  The last two times I've saved in the middle of a level, as soon as it gets me back to the lobby screen, the progress is gone and the level loads from the beginning.  After the first time, I was super careful to just let it save and go back to the menu, but instead of saying "Continue Campaign", it just says start campaign, and sure enough puts me back at the start.  Anyone else had this or know how to remedy the problem? FWIW I am connected to LIVE the whole time. 
 
Thanks