Why would my database revert to an earlier version

My colleague just logged in to one of our sites and found that the last 6 months worth of posts, etc. were missing.

I examined the database and saw that it had reverted to on old version. I have no idea why or how this happened. I have restored from backup but I want to understand how it happened so I can ensure it doesn’t happen again.

We’re running the latest WP and BuddyPress along with a variety of plugins:

– WordPress backup to Dropbox

– YARPP

– BP Registration

– Autochimp

– HGK SMTP

– Star ratings

and some others

The theme is Mingle and we’re on a shared host.

Any ideas that could help me figure this out much appreciated.