> Thanks for your replies.  What is the diff between snapshot 
> vs starting fresh?

You can use the argument provided in the startUp: method. This will tell
you if the image was started freshly or if it is continuing after a
save.

> If I'm backing up data from my image, I need to know when the 
> image has "quit without save" or crashed,

That's essentially the problem I was describing. However,

> because in that case, the backup data on 
> disk is probably more recent than the data in the image.

you could test this explicitly by adding a time stamp to your backup
data and remember it in the image. Upon saves, it will become persistent
so that whenever you start the image you can check the backup against
the time stamp and perform the appropriate action.

Cheers,
  - Andreas