I did some research on this message and this is basically what I found was that in some cases it is caused by insufficient disc space.
I found some information regarding this error on Jeremy Tammik's blog "The Building Coder" where he talks about when Revit was first developed in the US it was based upon Imperial units. When Metric and other units were introduced into Revit the basic existing database (based upon Imperial) remained.
Jeremy mentions "When Revit's API was introduced, the simplest method of introduction was to expose the database values directly. Thus feet for length, metric for everything else".
Thus I believe the reason for the verbiage of the error message.
Just got this reply from Autodesk Technical Support...
It was quite a quick response from Autodesk.