I ran into an interesting problem after "updating" an MS Access 2003 database into MS Access 2007 format. I had already implemented many of the new features, and then found out that I needed to also create a 2003 version (for users who would not be upgrading for a month or two)...
When I tried to Save As, I got the following error message:
You cannot save this database in an earlier version format, because it uses features that require the current file format.
Features that require the current file format include attachments, multivalued fields, offline data, or links to external files that are not supported by earlier versions of Access.
Sorry that this forum topic isn't posed as a question -- I already figured out the solution through trial and error. I just wanted to share my knowledge (since I couldn't find much information out there)
Cause: I had modified a system table to hide the Office 2007 ribbon. How to Hide The Ribbon
Solution: copy-paste all of the Forms, Queries, Reports, Macros, Modules and (non-system) Tables into a new 2007 database. Then Save As...