Anyone figure this out? Having the same issue, and I know the document is not locked.
So I had the same problem....at 1 AM..to setup tablets for the morning! Not cool.
I went back to basics and added a layer at a time and tested the mxd against the CreatMobileCache tool.
2 possibilities: it did not like some data that was in geographics (unlikely though).
There was 1 point file that was causing the error. Check Geometries did not find any issues, so I used Copy Features and created a new feature class.
And that worked!
Well done ESRI for providing useless documentation once again.
Ya, I never found a solution. We ended up getting a different data dump and it is working now. Have no real idea of the problem, just that everything indicates it was geo-db related