10.9.3 won't recognize my Seagate external Time Machine drive...

Question

I've already used Disk Utility. The hard drive shows up, but the volume itself is greyed out. When I repair the hard drive, this is the message I get:
Verifying and repairing partition map for “Seagate FA GoFlex Desk Media”
Checking prerequisites
Checking the partition list
Adjusting partition map to fit whole disk as required
Checking for an EFI system partition
Checking the EFI system partition’s size
Checking the EFI system partition’s file system
Checking all HFS data partition loader spaces
Checking booter partitionsReviewing boot support loaders
Checking Core Storage Physical Volume partitions
Updating Windows boot.ini files as required
The partition map appears to be OK
When I repair the volume ("Armand"), this is the response:
Verifying volume “Armand”
Checking file system
Error: This disk needs to be repaired. Click Repair Disk.
Verify and Repair volume “Armand”
Checking file systemVolume repair complete.Updating boot support partitions for the volume as required.
Error: Disk Utility can’t repair this disk. Back up as many of your files as possible, reformat the disk, and restore your backed-up files.
So...help? The hard drive hasn't been dropped, jostled, or anything like that. I'm using a MacBook Pro, Retina, 13-inch, Early 2013. This is really annoying, as I'd normally have just migrated my information from the last backup, done this morning!

Answer 1

The issue with WD drives started with Mavericks. WD does have a fix. You need to remove the WD software and update.
WD Drive Manager needs to be updated on Mac OSX 10.9.X (Mavericks)
Dear WD Registered Customer,
On October 30th, 2013 Western Digital informed registered customers of affected products via E-mail regarding reports of Western Digital and other external HDD products experiencing data loss when updating to OS X Mavericks (10.9). Our investigation to date has found that for a small percentage of customers that have the WD Drive Manager, WD Raid Manager and/or WD SmartWare software applications installed on their Mac, there can be cases of a repartition and reformat of their Direct Attached Storage (DAS) devices without customer acknowledgement which can result in data loss.
WD has been tracking this issue closely through our WD Forum and through our Technical Support hotline and the occurrence rate of this event has been very low. A specific set of conditions and timing sequences between the OS and the WD software utilities has to occur to cause this issue. SHOULD THIS EVENT OCCUR, THE DATA ON THE PRODUCT CAN LIKELY BE RECOVERED WITH A THIRD PARTY SOFTWARE UTILITY IF THE CUSTOMER STOPS USING THE DEVICE IMMEDIATELY AFTER THE OS X MAVERICKS (10.9) UPGRADE. WD will be issuing updated versions of these software applications that resolve this issue.
WD strongly urges our customers to uninstall these software applications before updating to OS X Mavericks (10.9), or delay upgrading until we provide an update to the applications. If you have already upgraded to Mavericks, WD recommends that you remove these applications and restart your computer. If you have already upgraded to Mavericks and are experiencing difficulty in accessing your external hard drive, please do not save anything to the drive, disconnect the drive from your computer, and contact Western Digital Customer Service at http://support.wd.com/country/ .