[AAfan]

Hi,
If the tools did not provide a bunch of error messags, then I doubt this is any completely new format. My guess is that either you are using an older version of the tools or this file has slightly different handling of the encoding or trailing data info than what the tools expect.

Please make sure you are using tools_v4.6 and that you have removed any old K4MobiDeDRM plugins and Mobi plugins from Calibre. If you still have problems, I would do as the plugin ReadMe states and try the calibredb add command to generate a log of the error messages and post them to the comments at the ApprenticeAlf blog where the authors of these plugins can see it and have a chance to look at it.

Asking at the source of the tools (where the tools authors can be found) on the ApprenticeAlf site is a better place to get these types of problems resolved.