BTW, I ran the process again and enabled logging. I turned on both the GUI logging mode, and enabled the debug-logging for the specific conversion of the MOBI version to Epub. Conversion still fails, and no error is reported in Calibre during conversion. But after the conversion appears to finish, no content comes through in the resulting Epub file (which is only 25K, rather than the ~ 25 MB that it should be). As you can see below, the log files reveal some problems.
I suspect the issue in this conversion must be due to the Bible's size, rather than to anything else. All my other Mobi-to-Epub conversions worked great, and like I said above, I've already verified that this file is non-DRM'd and that the source file is clean and uncorrupted.
Here are partial log file contents from running the GUI in logging mode:
calibre Debug log
calibre 0.7.36
Windows-7-6.1.7600
Windows
('Windows', '7', '6.1.7600')
Python 2.7.0
Windows: ('7', '6.1.7600', '', 'Multiprocessor Free')
Starting up...
Started up in 12.7660000324
Job: 1 Convert book 1 of 1 (Bible) finished
Convert book 1 of 1 (Bible)
Resolved conversion options
calibre version: 0.7.36
{'asciiize': False,
'author_sort': None,
'authors': None,
'base_font_size': 0.0,
'book_producer': None,
'change_justification': u'original',
'chapter': u"//*[((name()='h1' or name()='h2') and re:test(., 'chapter|book|section|part|prologue|epilogue\\s+', 'i')) or @class = 'chapter']",
'chapter_mark': u'pagebreak',
'comments': None,
'cover': 'c:\\users\\UserName\\appdata\\local\\temp\\calibr e_0.7.36_tmp_b4x6aj\\calibre_0.7.36_rwja6u.jpeg',
'debug_pipeline': u'C:\\Users\\UserName\\Calibre-debug',
'disable_font_rescaling': False,
'dont_split_on_page_breaks': False,
'epub_flatten': False,
'extra_css': None,
'extract_to': None,
'flow_size': 260,
'font_size_mapping': None,
'footer_regex': u'(?i)(?<=<hr>)((\\s*<a name=\\d+></a>((<img.+?>)*<br>\\s*)?\\d+<br>\\s*.*?\\s*)|(\\s* <a name=\\d+></a>((<img.+?>)*<br>\\s*)?.*?<br>\\s*\\d+))(?=<br>)' ,
'header_regex': u'(?i)(?<=<hr>)((\\s*<a name=\\d+></a>((<img.+?>)*<br>\\s*)?\\d+<br>\\s*.*?\\s*)|(\\s* <a name=\\d+></a>((<img.+?>)*<br>\\s*)?.*?<br>\\s*\\d+))(?=<br>)' ,
'html_unwrap_factor': 0.4,
'input_encoding': None,
'input_profile': <calibre.customize.profiles.KindleInput object at 0x05713BD0>,
'insert_blank_line': False,
'insert_metadata': False,
'isbn': None,
'keep_ligatures': False,
'language': None,
'level1_toc': None,
'level2_toc': None,
'level3_toc': None,
'line_height': 0.0,
'linearize_tables': False,
'margin_bottom': 5.0,
'margin_left': 5.0,
'margin_right': 5.0,
'margin_top': 5.0,
'max_toc_links': 50,
'minimum_line_height': 120.0,
'no_chapters_in_toc': False,
'no_default_epub_cover': False,
'no_inline_navbars': False,
'no_svg_cover': False,
'output_profile': <calibre.customize.profiles.KindleOutput object at 0x05713DF0>,
'page_breaks_before': u"//*[name()='h1' or name()='h2']",
'prefer_metadata_cover': False,
'preprocess_html': False,
'preserve_cover_aspect_ratio': False,
'pretty_print': True,
'pubdate': None,
'publisher': None,
'rating': None,
'read_metadata_from_opf': 'c:\\users\\UserName\\appdata\\local\\temp\\calibr e_0.7.36_tmp_b4x6aj\\calibre_0.7.36_gmvhxn.opf',
'remove_first_image': False,
'remove_footer': False,
'remove_header': False,
'remove_paragraph_spacing': False,
'remove_paragraph_spacing_indent_size': 1.5,
'series': None,
'series_index': None,
'smarten_punctuation': False,
'tags': None,
'timestamp': None,
'title': None,
'title_sort': None,
'toc_filter': None,
'toc_threshold': 6,
'use_auto_toc': False,
'verbose': 2}
InputFormatPlugin: MOBI Input running
on C:\Users\UserName\Calibre Library\[Remainder of path]
Extracting text...
Adding anchors...
Extracting images...
Cleaning up HTML...
Parsing HTML...
Malformed markup, parsing using BeautifulSoup
Markup contains multiple <html> tags, merging.
Converting style information to CSS...
Creating OPF...
Input debug saved to: C:\Users\UserName\Calibre-debug\input
Parsing all content...
Parsing styles.css ...
Parsing bible.html ...
Forcing bible.html into XHTML namespace
Generating default TOC from spine...
Parsed HTML written to: C:\Users\UserName\Calibre-debug\parsed
Merging user specified metadata...
Detecting structure...
Auto generated TOC with 0 entries.
Structured HTML written to: C:\Users\UserName\Calibre-debug\structure
Flattening CSS and remapping font sizes...
Source base font size is 12.00000pt
Cleaning up manifest...
[I removed a whole bunch of lines here about trimming images.]
Processed HTML written to: C:\Users\UserName\Calibre-debug\processed
Creating EPUB Output...
Rescaling image from 836x1200 to 429x616 cover.jpeg
Looking for large trees in bible.html...
No large trees found
This EPUB file has no Table of Contents. Creating a default TOC
EPUB output written to c:\users\UserName\appdata\local\temp\calibre_0.7.3 6_tmp_b4x6aj\calibre_0.7.36_cfa05l.epub