The Security Mentor

If you have compressed folders (you would have had to turn it on explicitly), then you may get files damaged if you create them in the compressed folder after installing one of the August security updates. There's no clear diagnosis yet, but a lot of consistent reports from the field. Confusingly, it doesn't happen to all files, just some of them.

The cleanest way to avoid this is to turn off compression on your folders for now. Some people have uninstalled the patch for security bulletin MS06-049 but I don't recommend that.