Unable to complete backup. An error occurred while creating the backup folder.

Same problem here- LaCie 2TB drive.

I went from plugged to the hub (on Time Capsule) to directly to the Mac - Erased the drive completely (with Disk Utility). The backup started fine, then after a few hours stopped with the "Unable to complete backup. An error occurred while creating the backup folder." (By the way: That's not enough info for an error message).

I expect more on a problem that has been reported for a while now.

See my post above. Time machine has been doing what it it's supposed to do until 13 July 2012 but now is giving the same error meassge as everyone else who's posting. I wonder if anyone at Apple ever reads these posts. Is there anybody out there?

I contacted Apple Support and the very pleasant chap who answered got me to disconnect the removable, turn Time Machine off, shut down the computer, unplug the power cord, plug it back in then restart while resetting the parameter RAM (option+command+P+R). You should get two start up chimes and it might take a couple of goes to do it. Did all that and Time Machine did what it's supposed to do. The chap also mentioned that such removables are not constructed as 'enterprise level' drives and shouldn't run continuously, which mine had been. So now I unplug it (not just eject it) every night. That kinda fixes the problem, but after a day, I still sometimes get the "unable to complete..." message but it's OK the next morning.

Interestingly, he wasn't aware of this problem because Apple doesn't read this stuff. I think he reckoned that it was mostly carping, wingeing & flaming, so the message is don't do it - it is anti-productive.

Also interestingly, this problem seems to coincide with installing Lion.

I had a similar problem. Not long after upgrading to Lion 10.7.5, I purchased a new 2T G-drive and after three back-up cycles, got the same message as Mr. Smalley. Repaired the drive with Apple Disk Utility, unmounted it and turned it off. Deleted the Time Machine .plist pref, re-attached drive, turned on the drive, turned on TIme Machine and did one backup, after which the next backup returned the same error message as before. Then I found and followed the instructions above - Turned off the external drive, unplugged it from the Mac, turned Time Machine off, shut down the computer (but did not unplug the power cord), started the computer holding down option+command+P+R till I heard the startup bong twice, then held down until I heard the third bong and let go all. After turning on the external drive, and plugging the Firewire 800 cable back into the Mac, turning on Time Machine, and selecting the G-drive as the backup-location, everything works fine now for four hourly back-up cycles so far. I hope this has solved the problem. I intend to keep the backup drive running 24/7. Thanks to Bill Smalley for providing these details.

For what it's worth:

I'm running OS 10.6.8, as are many others. So, it's not a 10.7 problem necessarily; nor a particular brand or type of external HD.

I find that hourly backups are superflous. No doubt others need that function, especially if your Mac is used for work. For a couple months I used TimeMachineEditor.app and did backups just daily, not hourly. For the most part, the error messages stopped.

I've now gone one step further. I don't even use TM Editor.app. I just turned TM off and once a day, usually when I first crank it up, I click on the TM icon in the toolbar and choose "Backup Now". Or maybe again later if I've created docs, downloaded something, etc. No errors in over a month.

I also find that my external TM drive gets fairly hot, even when it's just sitting there not doing any backups. So, on most days, after I've done my morning backup, I'll eject it and turn it off.

Again, I realize my methods only apply to the 'casual' user and not to someone who really needs to do hourly backups.

Since joining this conversation some time ago, I have discovered that if I unplug the external HD and leave it overnight to take a good hard look at itself, it will do what it's supposed to do, so that's what I do. But if it's plugged in for too long, I get the 'Unable to...' message. Interestingly, I don't have the same problem with external backing up a laptop.

@Bill Smalley writes,

"…I contacted Apple Support and the very pleasant chap …also mentioned that such removables are not constructed as 'enterprise level' drives and shouldn't run continuously…"

Doesn't that seem a little ludicrous seeing as how TimeMachine was created to be used on external HDDs…that stay connected and run pretty much continuously? Otherwise, how can it do hourly backups? Just one o' those thangs, I reckon, where some Macsters have problems with an app but the majority don't seem to. I still think for those of us who continue to having the problem that fewer backups and ejecting/shutting down the external HDD are the only solutions. As extensive as Pondini's fixes are, this one still isn't covered.