Editing block appears to delete ALL work

Hello,

I have run into a huge problem…

This has happened a few times now, and is both incredibly stressful and potentially disastrous for my work.

what appears to be happening is that when I edit a block, and then save the changes, for some reason it deletes ALL the work within the file I am working on…

I am working on files with a lot of information, i.e a years worth of work, so is really not nice… : [

fortunately I am working from drop box, and therefore I am able to go into the version history of the file and down load a version from a few minutes ago before the mass purging of my information…

please let me know if you need any more details for this…

thanks,

Andrew