this is my first post in this forum.. so please bear with my language..
I am running Windows 8 Pro (64bit) and Office 2010 SP1 (32bit) (both patched up to date) and have a Office 365 P1 subscription.

When I create a document from a SharePoint online document library,
the document opens the correct local app, i.e. Word 2010, allows me to edit,
but when I come to save the document back into SharePoint online, Word displays the following error:

Upload Failed. Your changes were saved but could not be uploaded because of an error. You may be able to upload this file using the server Web page.

It allows me to save the document locally and use SharePoint upload to manually upload the document, however this is not the method I am trying to use that should otherwise work from the client app.

I work with SharePoint in my professional career and I know that documents created in SharePoint should able to be saved directly back to the document library from where they were created from.

The Upload Center also displays an error for the document I have attempted to upload but simply states Upload Failed.

I have cleared the Document Cache, rerun the Desktop setup and reinstalled Office 2010 without success. The only thing I have not tried is using Windows 7, Office 2010 and Office 365.

Has anyone identified an answer to this issue?