My WD 1tb external is no longer being read by my macbook pro, and verification and repair keeps failing. I can't erase it either.
Try out the hard drive on another computer, to verify if it's a hard drive issue or a computer issue. Then, get another hard drive, or USB stick, and try reading/erasing/recording on it from your MAC, to see if the computer is handling external data storage devices properly.
I'm not a MAC guy so I can't help out if it's your computer that's misbehaving... but if it's the hard drive that's misbehaving, then you may want to run a partition repair scan and also run a surface-level scan to make sure everything's ok. If you have a PC near by, get the WD Diagnostic utility here http://www.softpedia.com/get/System/Hard-Disk-Utils/Western-Digital-Data-Lifeguard-Diagnostics.shtml and run an extended disk test. This will find and repair any logical problems with the hard drive. After the test is over, run a SMART scan too, that will tell you the physical state of the hard drive. If it points to some parameters that are off the recomended values you may want to get all the data off the drive. I'm sorry to say, but the 500GB-1TB Western Digital hard drives, especially the Green Line series, proved to be a very silky line, fragile, unreliable.
If you opt for a new hard drive, I suggest that you keep the WD casing, and stick a Samsung or a Seagate hard drive.
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