External hard drive ejects on sleep

I'm hoping I don't need to buy four new drives to 'fix' a problem caused by Mountain Lion.

Little Nelle, what brand of hard drive did you buy and which port (USB 2.0, 3.0, Firewire 800) are you using on your Mac?

I use an iMac 2010 with Mountain Lion. I bought a Seagate Backup Plus, 2 TB, with a USB port connection ($129). It's running beautifully and I had no problems transferring all of my data from the old external drive that was ejecting.

Thanks. I tried the "deselecting hard drive sleep" so we'll see if that works.

ok so here's my problem. i just took delivery on a brand new macbook pro with mountain lion os10.8.2, and plugged in my VERBATIM 500gb external hard drive, to the usb port. it has all my backup documents from my old macbook pro which has lion , os10.7.

like everyone else, things were working fine unti the computer went to sleep. upon waking, the hard drive had completely disappeared from the finder; i pulled it out, got the 'fail to safely eject...' error message, then got the more disturbing 'fail to repair the disk' error message. boom. there goes my all my backup documents.

i restarted a few times--sometimes with the external hard drive plugged in, sometimes with it unplugged-- repaired disk permissions, all to now avail.

i've seen on some of these posts advice to get firmware updates on the external hard drives, or to replace the hard drives, but really, apple? really??? is this hard drive shot? if so, then you owe me a new external hard drive.

in the meantime, must i plug it back in to my older, slower macbook pro and send this new one back for a full refund?? really, apple?

Couldn't agree more. Currently ejecting a Freecom 500GB, a wester digital green 2TB in caddy and a Samsung 2TB in caddy. Brilliant stuff. Sleeping my mac is now pointless.

I have the same problem with some USB and a network drive. This is a serious Mountain Lion problem.

Add me to this list of people with this problem.

Mac Pro 4,1

OS 10.8.2

Seagate 750 gb USB drive pluged directly into the Mac Pro

The drive is used for Time Machine. It doesn't seem to harm the drive but it shouldn't be happening.

I've not had time to check it on my own system, but has the latest OSX Supplemental update had any effect on this problem for anyone?

I'm running the latest regular release, OS X 10.8.2 (12C60) and the problem still exists.

I'm running this OS X 10.8.2 (12C3006) which now includes the Supplemental update they put out a few days ago. we'll see!

I just bought a WD Passport USB drive and I'm having exatcly the same problem. The drive is connected to USB hub of my ACD and everytime the Mac goes to sleep I get the "improperley unmounted" message. On my previous LaCie drive, which died long time ago, this didn't happen. What can I do ?

This is happening to me too. I also have a 1TB 2 partitions external hard drive.

"

I'm running this OS X 10.8.2 (12C3006) which now includes the Supplemental update they put out a few days ago. we'll see!"

Still ejecting the hard drive!

Same for me (10.8.2 on 2012 macbook air 11') except that the drives are well remounted. I still get the error message and guess that umounting is not correctly done...

I'm not comparing to any previous version because I got my macbookair with ML but it's very annoying...For an OS which compares himself to windows as much better, it makes me think that success and benefits of a company don't help making software better...

As a developer my last hope would have been to try patching the code but guess what, osx is not open source...

OSX people, please help your customers ;-)