Hi everyone, I have just received this message in Disk Utility when trying to "repair disk" on my main external HD. Any idea what this means? Its extra concerning because when I checked my time machine backup disk it also returned the same message... And a third External HD has all buttons greyed out so that I can't repair or verify (although I can with the single partition). This indicates to me that something other than the health of the individual disks might be the issue... unless its a huge coincidence? I've got 4 main external HDs that I repair/verify regularly and I've never seen this message before so it would seem highly unlikely that it would happen to 2 HDs simultaneously for the first time... I get the same message from disk utility on my other computer. Could it be a virus? I used terminal to get the following results based on instructions from another website (In the Terminal window, give it the following commands, one per line, pressing the Return key at the end of each line: diskutil list diskutil cs list mount): Dustins-Mac-Pro-2:~ dustinmclean$ diskutil list /dev/disk0 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *251.0 GB disk0 1: EFI EFI 209.7 MB disk0s1 2: Apple_HFS Macintosh HD 250.1 GB disk0s2 3: Apple_Boot Recovery HD 650.0 MB disk0s3 /dev/disk1 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *4.0 TB disk1 1: Apple_HFS 4TB 4.0 TB disk1s1 /dev/disk2 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *4.0 TB disk2 1: Apple_HFS TIME MACHINE 2 4.0 TB disk2s1 /dev/disk3 #: TYPE NAME SIZE IDENTIFIER 0: FDisk_partition_scheme *2.0 TB disk3 1: Apple_HFS Samples 2.0 TB disk3s1 Dustins-Mac-Pro-2:~ dustinmclean$ diskutil cs list No CoreStorage logical volume groups found Dustins-Mac-Pro-2:~ dustinmclean$ mount /dev/disk0s2 on / (hfs, local, journaled) devfs on /dev (devfs, local, nobrowse) map -hosts on /net (autofs, nosuid, automounted, nobrowse) map auto_home on /home (autofs, automounted, nobrowse) /dev/disk1s1 on /Volumes/4TB (hfs, local, nodev, nosuid, journaled, noowners) /dev/disk3s1 on /Volumes/Samples (hfs, local, nodev, nosuid, journaled, noowners) /dev/disk2s1 on /Volumes/TIME MACHINE 2 (hfs, local, nodev, nosuid, journaled) Thanks in advance!