Hi Dave Thanks for responding. No, the files and project are kept on a separate USB 3 external drive. Vegas is on the main C drive. There has to be something with Vegas, because if I put the files in another program, eg Cyberlink Power Director, then I don’t have any problems. It only happens when the files are being worked on in Vegas. And today the problem got a little worse because now the problem has crept into the render process so that when I tried to render my latest project, the video became corrupted about half-way through the project (and it’s only a 12 minute project). Didn’t have this problem previously and there was no issue with rendering a 40/50 minute project. There’s clearly something Vegas 12 doesn’t like. I tried downloading the program again and re-installing it – but that didn’t help!