Samsung Galaxy S3 — E: failed to mount and various other error messages

G'day all,

I have a Samsung Galaxy S3 (GT-I9300) which until yesterday morning was working fine. At 5am it beeped and when I looked at the screen it was stuck on the boot up screen showing Samsung Galaxy S3 - GT-I9300. The phone has never been altered from the factory stock ROM and no new apps have been added recently.

I spent all day yesterday trying to use the Android System Recovery options (Wipe data/factory reset) as well as trying to load new ROM from Odin, all with no success.

When in the Android system recovery menu, the following text is displayed line after line (all in red)

E:failed to mount /cache (Block device required)
E:Can't mount /cache/recovery/log
E:Can't open /Cache/recovery/log
E:failed to mount /cache
etc etc

If I try to wipe data/factory reset the same text appears with some more referencing the E drive not being able to be opened etc.

Has anyone else got any ideas what to try next? I live in a small rural town (2000km from nearest large city) and I called Samsung service centre who told me as the phone is an international model they can't assist in Australia anyway.

Thanks in anticipation of any assistance.