Could possibly be a currupt file. I'm trying to get a crash with your autoback file and I'm not able to reproduce. It would be good if we can find where or what caused the curruption.
I haven't used 2013, but usually this happens to me during Autosave/backup. When I'm working with a really high poly model, I'll change autoback from 5 minutes to 20.
yuh. happened a few times to me. Thank god Zbrush has an Autoback now. ^_^ I find the magic retopo really lends itself to a certain type of modelling. Going to give it another go today.
I usually have the autoback option enabled, it's been awhile since I worked with CE, should have paid attention. Oh well, gives me the chance to improve my scene's terrain I guess.