A family of Microsoft products that enable users to capture, organize, and reuse notes electronically.
Well, you have to eliminate the possibility that your server considers onenote as a virus.
Try to create a new notebook and sync some content to the sharepoint. If it goes through and works fine you probably have a virus or a restricted file pasted into your old oneNote.
There are some file-restrictions on sharepoint. make sure that you dont have any *.bat '.lnk files or so