Just registered because I'm having also the great mime-type error during validation.
I've created an C# application which creates a large Car Specifications ebook on the fly from a database source. For people who don't know C#. It's a windows application.
The whole creation of the ebook is ended by zipping the file doing the following:
Add mime-type file into a new zip file. (compression none)
close that file..
Open the same file and add the OPS and META-INF with the right files (compression Best)
The mimi-type file I'm using I took from another online epub book that's validated.
Well...this keeps on happening: ERROR: 123456.epub: mimetype contains wrong type (application/epub+zip expected)
I'm lost...nothing seems to work. Any body got a clue ?