Advice:

Never save a �big" package using monticello (lets say ~2000 classes)

and then save the image

Why?

Because while you don�t have feedback of saving progress* it will be doing something on background (forked save?) and if for any reason you are tempted to do an image save or save and quit, it will save in a state that will prevent the image from opening again

You have no option but to go to your previous image version or something of the kind

:(

*saving a package actually provides some feedback on progress but when the progress bar finishes, the saving doesn�t actually finish and it still have something going on, so you get "silence� (no-feedback) until you get the little monticello window with your new package version