Unable to edit an Excel spreadsheet and save back to confluence.

I'm attempting to edit an excel spreadsheet attachment from a Confluence page. Online doc states that I should be able to open, edit, and save back to confluence. I can open the file, but when i attempt to save, i get a message stating that the file is read only and that I have to save a local copy. I saw the issue that exists between Confluence and an earlier version of the Scaffolding plugin, but my confluence version is 3.1 and Scaffolding version is 3.4.1