I've never seen that message before. I really don't know what could be the issue.
I can only suggest that you re-download the bin file, then re-copy the file to your platform-tools folder.
Also, when you run the command, change the directory (cd command) to the platform-tools folder. I'm not positive, but you may not have adb and fastboot added to your environment variables. If this is the case you would not be able to run those binaries from outside the directory, and that may have caused the error.
I hope this helps.