A family of Microsoft word processing software products for creating web, email, and print documents.
I don't think you are doing anything wrong.
If you have a file open right now, just us SAVE AS to save it to your local HD to save your current changes.
Off the top of my head it sounds like an issue with your internet connection.
Try downloading the file to your local drive, then opening it in the application, make changes, save to local drive and finally upload to skydrive. That way your changes are safe if there is an internet problem. You have the option of repeating the upload until it works.