That bug has been opened on https://launchpad.net/distros/ubuntu/+source/gnome-system-tools/+bug/47440

"disks-admin shows 'not accessible' for many partitions (though not for all) when used in a live system (desktop CD); furthermore, it can not used to access NTFS partitions (the Browse button starts nautilus, nautilus shows an error 'do not have the permissions ...')

after installation, disks-admin works but is not needed anymore; all available partitions are mounted, clicking on the partition icons on the desktop opens a nautilus window with the content of the partition; this works fine now

to summarize:

- in a live system, disks-admin does not work in most cases

- in a installed system, disks-admin is no more needed

perhaps the easiest solution would be to drop it ...
...
> Thanks for the report.

Could you list the types of the partitions which disks-admin is able to show/not show?
...


fdisk -l

Disk /dev/hda: 123.5 GB, 123522416640 bytes
255 heads, 63 sectors/track, 15017 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot Start End Blocks Id System
/dev/hda1 * 1 1912 15358108+ 7 HPFS/NTFS
/dev/hda2 1913 12111 81923467+ 7 HPFS/NTFS
/dev/hda3 12112 12234 987997+ c W95 FAT32 (LBA)
/dev/hda4 12235 15016 22346415 f W95 Ext'd (LBA)
/dev/hda5 12235 15016 22346383+ 7 HPFS/NTFS

Disk /dev/hdb: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot Start End Blocks Id System
/dev/hdb1 * 1 10527 84558096 5 Extended
/dev/hdb5 1 653 5245159+ 83 Linux
/dev/hdb6 654 849 1574338+ 82 Linux swap / Solaris
/dev/hdb7 850 1372 4200966 83 Linux
/dev/hdb8 1373 1881 4088511 83 Linux
/dev/hdb9 1882 2518 5116671 83 Linux
/dev/hdb10 2519 3005 3911796 83 Linux
/dev/hdb11 3006 3492 3911796 83 Linux
/dev/hdb12 3493 4145 5245191 83 Linux
/dev/hdb13 4146 5059 7341673+ 83 Linux
/dev/hdb14 5060 6154 8795556 83 Linux
/dev/hdb15 6155 7371 9775521 83 Linux
/dev/hdb16 7372 8155 6297448+ 83 Linux
/dev/hdb17 8156 8884 5855661 83 Linux
/dev/hdb18 8885 9613 5855661 83 Linux
/dev/hdb19 9614 10527 7341673+ 83 Linux

for this system, only one partition is accessible in disks-admin

/dev/hda2

I tested this for other systems as well with similar results; I found no pattern which partitions are accessible and which not"