[ubuntu-za] Mount / Unmount Help

[Barry Wyatt]

I have a physical HDD - /dev/sdb1

All of a sudden I can't access it. I get the error message: Unable to
mount the volume.
Details say "Cannot create mount directory"

In GParted when I try to unmount the volume it says:
Could not unmount /dev/sdb1
The partition could not be unmounted from the following mountpoints:

/

Most likely other partitions are also mounted on these mountpoints.  You
are advised to unmount them manually.

Of course it is full of data which I don't want to lose.
Any ideas how I get it back without losing things?
Any ideas as to why this happened?

Thanks in advance,
Barry