LG external hard drive previously working OK now presents 'cannot mount volume'

When you last unplugged it, did you use the 'safetly remove' feature of your OS?
What format is the partition?

What is the output of:

lsb_release -a; uname -a

Thanks

No I did not see a safety remove feature anywhere.
Sorry but I don't understand the other questions - I'm a complete novice

I'm using Ubuntu Jaunty Jackalope if that's any help. Maybe I am having problems because I have not been able to take updates for some time

Jaunty is EOL. I suggest you upgrade to a fresh install of Precise. Not only is it the latest stable release of Ubuntu, it is also LTS so is supported til 2017. There is a safe remove feature for external strages in ALL modern OSes, Ripping the drive out will garbage the data and can damage the device. There is a reason why it is coded in. The caches need to be flushed and the OS needs to forget the device so that removal does nothing adverse.

Windows XP:
http://media.wiley.com/Lux/14/79114.image0.jpg

Ubuntu:
http://4.bp.blogspot.com/_JBHfzEovWs8/TMbVRcY2RaI/AAAAAAAAAyg/ijHUWJfZCQ8/s1600/safelyremovedeviceubuntudefault.png

Vista:
http://media.wiley.com/Lux/08/91908.image0.jpg

And so forth, you MUST use these.

OK, I will look at all the information that you have supplied.
Thank you very much for your time and effort, it is much appreciated.

On Wed, Aug 22, 2012 at 2:21 PM, actionparsnip <
<email address hidden>> wrote:

> Your question #206498 on yelp in Ubuntu changed:
> https://answers.launchpad.net/ubuntu/+source/yelp/+question/206498
>
> Status: Open => Answered
>
> actionparsnip proposed the following answer:
> Jaunty is EOL. I suggest you upgrade to a fresh install of Precise. Not
> only is it the latest stable release of Ubuntu, it is also LTS so is
> supported til 2017. There is a safe remove feature for external strages
> in ALL modern OSes, Ripping the drive out will garbage the data and can
> damage the device. There is a reason why it is coded in. The caches need
> to be flushed and the OS needs to forget the device so that removal does
> nothing adverse.
>
> Windows XP:
> http://media.wiley.com/Lux/14/79114.image0.jpg
>
> Ubuntu:
>
> http://4.bp.blogspot.com/_JBHfzEovWs8/TMbVRcY2RaI/AAAAAAAAAyg/ijHUWJfZCQ8/s1600/safelyremovedeviceubuntudefault.png
>
> Vista:
> http://media.wiley.com/Lux/08/91908.image0.jpg
>
> And so forth, you MUST use these.
>
> --
> If this answers your question, please go to the following page to let us
> know that it is solved:
>
> https://answers.launchpad.net/ubuntu/+source/yelp/+question/206498/+confirm?answer_id=4
>
> If you still need help, you can reply to this email or go to the
> following page to enter your feedback:
> https://answers.launchpad.net/ubuntu/+source/yelp/+question/206498
>
> You received this question notification because you asked the question.
>

Thanks actionparsnip, that solved my question.