I build a simple App with Xcode 7.1.1, archive it and export it with the organizer as a .ipa file. When I try to upload this ipa to ituneconnect with Application Loader 3.3. with DAV protocol only, the application Loader fails with a mysterious "An error occurred uploading to the App Store". On itune Connect the build is available in the Activity section with an forever "Processing" state. When I upload with Signiant protocol, everything works fine...
FYI, I do need the DAV protocol as I'm behind a firewall in normal situation without rights on it.