Just thought I'd share this, in case someone else comes across the same issue.
BackupPC-3.3.1-1.el7.x86_64 on CentOS 7.1
After a nightly yum update, which updated smbclient to 4.2.10, all SMB backups of my NetApp filers stopped working with the error below:
2016-04-20 15:00:04 full backup started for share backup1
2016-04-20 15:00:07 Got fatal error during xfer (session setup failed: NT code 0x80090302)
2016-04-20 15:00:16 Backup aborted (session setup failed: NT code 0x80090302)
The fix was to change the smb backup command, adding --option=clientusespnego=no, like so:
$smbClientPath --option=clientusespnego=no \\$host\$shareName $I_option -U $userName -E -d 1 -c tarmode\ full -Tc$X_option - $fileList
Cheers,
Otto