Not saving files-My Book Essential

After the latest update, files will not save to the disc

My Book Essential also stopped saving on backup.  Error message says “disk not readable by computer”.  In Finder, WD Smart Ware shows  and Disk s1s or something like that shows.  Time Machine of course is not working now.  So suddenly my external HD has quit.  Any ideas?  I’m running Mavericks 10.9.2, 2.4Ghz/4G.