The error indicates the file is damaged. You can try to decrypt it anyway, you’ll find instructions at http://www.axantum.com/ where you can find a registry setting to enable it to try even with a broken file.
The version you are using is unsupported and unmaintained, but you will find information as mentioned above.
There should be no link to “axcrypt dot com” on any FAQ we have – can you give a URL to that page? (We’ve never actually had that domain).