Time Machine cannot find external toshiba hard drive after OS X 10.9.2 update I used my Toshiba Canvio USB 3.0 external hard drive without any problems for the past year.  Today, I received a system alert:


  Backup failed. The backup disk "Time Machine Backups" is not available


Other Mavericks OS users with similar issues. from apple.com forums

My Console output is below: 

4/24/14 10:26:52.131 PM com.apple.launchd[1]: (com.hidden.daemon[579]) Job appears to have crashed: Trace/BPT trap: 5
4/24/14 10:26:52.131 PM com.apple.launchd[1]: (com.hidden.daemon) Throttling respawn: Will start in 10 seconds
4/24/14 10:26:52.189 PM ReportCrash[559]: Saved crash report for Hidden[579] version ??? to /Library/Logs/DiagnosticReports/Hidden_2014-04-24-222652_MYMBPr.crash
4/24/14 10:26:53.515 PM com.apple.backupd[530]: Starting manual backup
4/24/14 10:26:53.515 PM com.apple.backupd[530]: Error -35 while resolving alias to backup target
4/24/14 10:26:53.518 PM com.apple.backupd[530]: Backup failed with error 18: The backup disk could not be found.
4/24/14 10:26:53.704 PM com.apple.launchd.peruser.503[193]: (com.hp.help.tocgenerator) Throttling respawn: Will start in 10 seconds
4/24/14 10:26:54.553 PM com.apple.launchd.peruser.503[193]: (com.hp.help.tocgenerator) Throttling respawn: Will start in 10 seconds
4/24/14 10:27:02.352 PM com.apple.launchd[1]: (com.hidden.daemon[588]) Job appears to have crashed: Trace/BPT trap: 5
4/24/14 10:27:02.352 PM com.apple.launchd[1]: (com.hidden.daemon) Throttling respawn: Will start in 10 seconds
4/24/14 10:27:02.408 PM ReportCrash[559]: Saved crash report for Hidden[588] version ??? to /Library/Logs/DiagnosticReports/Hidden_2014-04-24-222702_MYMBPr.crash
4/24/14 10:27:04.790 PM com.apple.launchd.peruser.503[193]: (com.hp.help.tocgenerator) Throttling respawn: Will start in 10 seconds
4/24/14 10:27:06.125 PM com.apple.launchd.peruser.503[193]: (com.hp.help.tocgenerator) Throttling respawn: Will start in 9 seconds
4/24/14 10:27:12.565 PM com.apple.launchd[1]: (com.hidden.daemon[591]) Job appears to have crashed: Trace/BPT trap: 5


My Disk Utility shows the Toshiba External USB 3.0 Media hard drive as plugged in but it is greyed out. It shows S.M.A.R.T. Status: Not Supported, Partition Map Scheme: GUID Partition Table and Write Status: Read/Write.

Any ideas?
Go to /Macintosh HD > Library > Preferences, move to the trash the file com.apple.TimeMachine.plist and restart the Mac.

Open Time Machine Preferences and "Choose" or "Add" the disk as a Backup Disk. The following backup will be added to the existing ones.