Question Author
Thanks everyone for your advice. I ended up restoring my file from my backup, but unfortunately I lost about 3 weeks' work.
What I don't understand is I did a back up on 6/5/11, yet I only had the option of restoring from a backup dated 20/4/11. On my hard drive, there is the option of restoring files from 6/5, but now I'm not sure if that will cause me more trouble, as I had to spend a considerable amount of time updating some of the work I'd lost in the interim, and not sure if this option will bring back the files I backed up on the 6/5