Hi,
I updated to 1.4.0 but it appears that this update is not working at all for me. Every book I open (that validated fine previously and contains no epubcheck errors) suddenly aren't "well-formed" (but really, there is no error at all and the headers are the same on every xhtml file within a single file).
Here is a "well-formed" header:
And here is a "faulty" header (according to 1.4.0):
Unfortunately, as I need a few tools that are blocked by the "well-formed" validation, I'm forced to revert back to 1.3 for now...