Comment 14 for bug 442130

I have the same problem, but only using nautilus. pcmanfm works fine, just like nautilus used to in 9.04.

bash > uname -a
Linux serenity 2.6.31-16-generic #52-Ubuntu SMP Thu Dec 3 22:07:16 UTC 2009 x86_64 GNU/Linux

bash > gvfs-mount -oi
Monitoring events. Press Ctrl+C to quit.

(execute "nautlius --no-desktop", click on a partition, get popup saying "Unable to mount Pictures. Authentication is required". Close nautilus)

(execute pcmanfm, click on partition. It mounts! The log shows:)

Volume changed: 'Pictures'
  Volume(0): Pictures
    Type: GProxyVolume (GProxyVolumeMonitorGdu)
    ids:
     uuid: 'e7b03d12-913d-479e-a5a3-561e8624a6ce'
     unix-device: '/dev/sda5'
     label: 'Pictures'
    themed icons: [drive-harddisk-ata] [drive-harddisk] [drive]
    can_mount=1
    can_eject=0
    should_automount=0

Mount added: 'Pictures'
  Mount(0): Pictures -> file:///media/Pictures
    Type: GProxyMount (GProxyVolumeMonitorGdu)
    themed icons: [drive-harddisk-ata] [drive-harddisk] [drive]
    can_unmount=1
    can_eject=0
    is_shadowed=0

Just like in 9.04, I have no entry for this partition in /etc/fstab. I upgraded to 9.10, did not do a clean install.