I see this message too when I have 2 new, blank & unsaved documents open in 2 browser windows. I'm guessing Clearspace is confused since there are 2 new & unsaved documents open at the same time...
The Clearspace system saves the work you're doing in a draft state every n seconds that you've made a change so that if you're browser crashes or if your session times out you won't lose your document / blog post / discussion thread message. For the most part you shouldn't see the 'recovered version of this content exists...' message, but if you click 'create a document', choose a community, enter a title... and then close your browser, that document exists as a recovered document, which is maybe why you got the message.
I think this needs to be documented better in our online documentation because there are some interesting rules behind how / when drafts are created, here's an issue for you: