We have several OneNote 2010 notebooks on our SharePoint 2010 site each of which are edited by several users. This has worked for more than six months. Suddenly, users are getting an "Incomplete sync" error for some of the notebooks. Sometimes it is only for some sections (other sections sync just fine), and sometimes the error is for all sections. The error is 80070005, despite the fact that a password is entered.
After deleting the OneNote_RecycleBin from within SharePoint, sync started working for a bit, then died an hour or two later. Attempts to delete the recycle bin again haven't helped, so maybe that was coincidence.
We have made no changes to permissions or anything that we know of to the SharePoint site, and other notebooks within the same document library (sometimes even different sections of the problem notebook) continue to work fine.