Yup, looks like the "mimetype" file is missing (should be in the root of the ePUB file and not compressed). Also there should be a folder in the ePUB named "META-INF" with a "container.xml" file inside it.
The "mimetype" file is just a text document with no extension with this text inside it,
Code:
application/epub+zip
The "container.xml" is just a xml file with this text inside,
Code:
<?xml version="1.0"?>
<container version="1.0" xmlns="urn:oasis:names:tc:opendocument:xmlns:container">
<rootfiles>
<rootfile full-path="content.opf" media-type="application/oebps-package+xml"/>
</rootfiles>
</container>
These files are used by the ePUB reader to identify the file and show where the content manifest for the ePUB is.
Fixing might be as easy as opening the ePUB in Sigil and saving [UPDATE Nope, just tried it, causes Sigil to crash.] or exploding it in Calibre and adding the files/folders manually.
Here is a zip file with the files needed. In Calibre right click the book and select "tweak Book" then "Explode ePUB" in the dialog box, copy everything in the zip file into the folder that opens, close the folder, and click "Rebuild ePUB" in the dialog box.
Hopefully this helps.