Hi Louise
You'll need to provide a lot more information before anyone can help you.
Operating system?
Photoshop version?
File types that are being corrupted (.psd, .jpg etc.)?
What sort of hardware (desktop, laptop)? If laptop are you using battery or mains power?
Do you get many system crashes? Were the corrupt files being saved when a crash occurred?
What you were doing when these files become corrupted (saved and returned later)?
Any other relevant information?