Time Machine error creating the backup folder on a spacious hard drive I have upgraded recently to Mavericks, and am setting up Time Machine on this system for the first time (it wasn't set up with the earlier OS, Mountain Lion.)

Time Machine successfully backs up once after I boot the laptop.  However, every time it tries to back up again while the laptop is running (I don't normally perform a full shutdown and reboot very often!) it fails with the error message: "An error occurred while creating the backup folder."



I would like to eject the drive and plug it in again to see if this helps, but clicking the Eject button in Finder shows this message:



and I have not wanted to do a Force Eject.  I have rebooted, and Time Machine successfully backed up once after that, only to fail again the next time it tried.

I do sometimes close the laptop lid or put it to sleep with the disk still plugged in, and it is still there when it wakes.

I searched the Console for Time Machine-related errors but could not see any.  (The Console won't display system.log saying I don't have permissions, but running syslog -C in the Terminal and scanning the output doesn't show anything either.)

How do I:


Solve the issue, so it successfully create the backup folder
Perhaps, see if it is Time Machine or another app that is preventing the disk eject?


Details:


An early 2011 Macbook Pro, which was running Mountain Lion for a week on a new internal hard drive, now Mavericks
The drive is a 2TB Toshiba USB drive.  I formatted it at as Mac OS X Journaled.  Running Disk Utility and verifying the disk shows no errors.
The drive has about 800GB free space.
I am running from a normal (non-admin) user account.
I had the exact same symptoms with a Nov 2013 MacBook Pro (came with Mavericks already installed) using WD "My Passport" USB drives for Time Machine backups.  The solution was to erase and reformat the external drives using Disk Utility as described in
   http://support.apple.com/kb/HT5911 under the heading "Erase and reformat the storage device".

I had a spare drive so, in order not to lose existing backups, I did the following:


erase spare drive as above
use Disk Utility to "restore" the backup drive's volume to the erased drive
(you have selected the volume correctly (rather than the drive) if the Disk 
Utility window shows 
    "First Aid; Erase; RAID; restore" as options
not 
    "First Aid; Erase; Partition; RAID; restore")


After this I have no problem doing multiple backups in a row, putting the machine to sleep without ejecting the backup disk and then doing a further backup, and no problems with ejecting the disk.

Good luck!