I have re-done all of the work and had this happen to me THREE TIMES now. I have checked everything from system, to interacting software, to my virus scanner, to any hardware issues. This is enraging. I've now lost a client because of this.
I don't mean to be cruel here, but you lost a client because you didn't have a efficient and safe workflow set up. I never do anything without saving files in versions about every 10 to 20 minutes. If your files are getting corrupted every time you save them then you got to analyze your project and figure out what you are doing that is causing the corruption. Work for 10 or 15 minutes, save the file, open the file, save it as a different version then start again when you're having problems. Here's the most important part of business advice I can give you. As soon as you have any indication that there may be something wrong, contact your client. Don't make excuses, don't blame the software, take full responsibility and just explain that you need more time or something in the project needs to change. I have never had a client refuse to give me some leeway or refuse to make adjustments to the project that would allow it to be completed on time.