Why will OSX 6/9 not mount my drives?

[LetThisNightExplode]

I have a few hard drives in this mac pro tower 10.9 Mavericks - they show up in Disk Utility but will not mount. DU shows a sort-of "blank document" or "unidentified filetype" image instead of the normal icon for external media.

I used CCC to migrate data from a 3TB drive to a 4TB drive on a computer running a 10.8 Mountain Lion - and then (with the hard drives disconnected) upgraded that machine to 10.9 Mavericks. Since re-connecting, they will not mount. However, they will also no longer mount if I place them in a NAS connected to my MacBook Pro running 10.6 Snow Leopard.

Both yes, are over 2.2 TB in size.

They used to work before (and connected to each other via shared folders, etc, etc.

[SIZE=3]   /dev/disk0
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:      GUID_partition_scheme                        *250.1 GB   disk0
       1:                        EFI EFI                     209.7 MB   disk0s1
       2:                  Apple_HFS Sharp Island            249.7 GB   disk0s2
    /dev/disk1
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:      GUID_partition_scheme                        *3.0 TB     disk1
       1:                        EFI EFI                     209.7 MB   disk1s1
       2:                  Apple_HFS Media 2                 3.0 TB     disk1s2
    /dev/disk2
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:     FDisk_partition_scheme                        *1.0 TB     disk2
       1:               Windows_NTFS System Reserved         104.9 MB   disk2s1
       2:               Windows_NTFS                         1.0 TB     disk2s2
    /dev/disk3
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:     FDisk_partition_scheme                        *7.9 GB     disk3
       1:                 DOS_FAT_32 OSX TOOLS               7.9 GB     disk3s1
    /dev/disk4
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:     FDisk_partition_scheme                        *7.9 GB     disk4
       1:                  Apple_HFS OSX                     7.9 GB     disk4s1
    /dev/disk5
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:     Apple_partition_scheme                        *1.5 TB     disk5
       1:        Apple_partition_map                         32.3 KB    disk5s1
       2:                  Apple_HFS Sharp Island 3          1.5 TB     disk5s3
    /dev/disk6
       #:                       TYPE NAME                    SIZE       IDENTIFIER
       0:      GUID_partition_scheme                        *3.0 TB     disk6
       1:                        EFI EFI                     209.7 MB   disk6s1
       2:                  Apple_HFS Media 3                 3.0 TB     disk6s2[/SIZE]

disk0 is the System SSD - running smooth as butter. disk1 and disk 6 ("Medias") are the culprits. they will not mount and Disk Utility shows them as having "0 folders and 0 files" - although showing they're actual disk usage/capacity. disk 2 is a Windows installation (doubt its relevant though) disk 3 and 4 are USB sticks, and disk 5 is another drive equivalent to the "Medias"

here you can see the icons for those partitions does not load, either ..

Any help would be greatly appreciated! thank you!

 

[LetThisNightExplode]

It "mounts" with 0 files and folders - but you can see that the files are taking up space. It doesn't every actually show up in Finder either. - DiskUtility says I can "unmount" it but it never popped up into the Devices list in Finder. This is rather weird