Two teams here are seeing the same problem. We build .chm files with Flare and they are fine, then if we rename the .chm file the stylesheet and any included images can no longer be found.
This doesn't happen with every .chm file we build.
We've observed it with both command-line builds and interactive builds, but haven't figured out what variable(s) determine whether the file will display this problem or not.
We don't think it's cosmic rays

because one team has been doing nightly builds on a static source base and the problem seems to occur every time. (They were renaming the .chm file in their build script, so the .chm file in their product was corrupt. They've removed the renaming step so it is ok now, unless a customer decides to rename it.)
Has anyone else seen this? Have any idea what causes it?