What validator are you using? What's the error? Does this happen with just one EPUB or with more than one?
For a validator, I am using "validator.idpf.org/application/validate". Right now, I am working on just the cover for the epub—just one page made up of several images (from PS and Illus) grouped with text and rasterized in ID. No other text is on the cover as all text is part of the image, so maybe that is causing the error (the missing line of code is for <dc:language>)? I tried many different versions of the cover, but the error re-occurred each time. It validated successfully on OS 10.6.
The epub opens in Adobe Digital Editions, but validation shows the error and it will not convert to mobi without inserting the missing line of code. I have to unzip the epub to get to the content.opf file, add the code in TextEdit, then re-zip the epub.
Will be working on the rest of the epub and will see how that export goes.
The cover does not have any styles applied and I deleted all unused paragraph and character styles and deleted all unused layers in ID.
I upgraded to OS X10.8.5 a couple days ago so I could make full use of Creative Cloud (Typekit in particular). Love CC so far, but seeing some odd behavior on the new OS. Maybe I need to do more with XQuartz?
Thanks for confirming. I wondered about the no-text issue. I'll see how the epub document looks when I insert some text outside of the graphic. Easier than my current work-around!