So earlier today my daughter came to show me that the majority of her files and photos were empty. After quick check (i am by no means an expert with computers, so quick means approx 1hr!) i found a help_dec.txt file explaining her laptop had been subject to a Trojan type ransomware virus and without paying $500 all her files will remain encrypted with a high end encryption that is "impossible" to decode.
After another quick google search it appears this is a genuine virus and thousands of people have had similar problems.
Luckily in this case we could restore previous versions without problem and update virus protection software to include crypto checks (unbelievable that virus protection didnt actually protect - kudos to norton!)
Take care folks and remember to make regular backups.
Useful link:
http://www.bleepingcomputer.com/viru...re-information