My linux unzip -t says there are 52288 bytes of stuff at the beginning of the file, followed by files that look suspiciously like the source files for your mobi. Since Kindlegen now does tack the source files on at the end, I suspect that winrar is silently ignoring your mobi part and giving you back your source files. Mac users have a way of stripping the trailing source files, but I'm not sure it's been done for Windows (or Linux) users of Kindlegen.
The 12 files following add up to 72628 bytes, so they must be somewhat zipped up, at least. That's nice to know.
Last edited by pholy; 06-28-2011 at 09:35 AM.
Reason: Added total length of files following.