Microsoft OneNote 2013 on Windows 8 kept on asking for a password to sync a notebook to a local SharePoint site.
This was caused by a Windows 2008 domain controller not pushing domain policy settings to a Windows 8 client.
The Windows 8 client didn’t have the SharePoint site added to the local intranet zone.
Control panel > Internet Options > tab:Security > Local Intranet > Sites > Advanced
Uncheck "Automatically detect intranet network" and add your intranet sites: