CBR convert to EPUB failing.

[skullmonger]

I'm trying to convert a CBR to EPUB, in Win Vista, Calibre 0.7.44, but I get:

calibre, version 0.7.44
ERROR: Conversion Error: <b>Failed</b>: Convert book 1 of 1 (Herogasm 01)

Convert book 1 of 1 (Herogasm 01)
Resolved conversion options
calibre version: 0.7.44
{'asciiize': False,
'author_sort': None,
'authors': None,
'base_font_size': 0.0,
'book_producer': None,
'change_justification': 'left',
'chapter': None,
'chapter_mark': u'pagebreak',
'colors': 256,
'comic_image_size': None,
'comments': None,
'cover': None,
'debug_pipeline': None,
'dehyphenate': True,
'delete_blank_paragraphs': True,
'despeckle': False,
'disable_font_rescaling': True,
'disable_trim': False,
'dont_grayscale': True,
'dont_normalize': False,
'dont_sharpen': False,
'dont_split_on_page_breaks': False,
'enable_heuristics': False,
'epub_flatten': False,
'extra_css': None,
'extract_to': None,
'fix_indents': True,
'flow_size': 260,
'font_size_mapping': None,
'format_scene_breaks': True,
'html_unwrap_factor': 0.4,
'input_encoding': None,
'input_profile': <calibre.customize.profiles.InputProfile object at 0x05A21FB0>,
'insert_blank_line': False,
'insert_metadata': False,
'isbn': None,
'italicize_common_cases': True,
'keep_aspect_ratio': False,
'keep_ligatures': False,
'landscape': False,
'language': None,
'level1_toc': None,
'level2_toc': None,
'level3_toc': None,
'line_height': 0.0,
'linearize_tables': False,
'margin_bottom': 0,
'margin_left': 0,
'margin_right': 0,
'margin_top': 0,
'markup_chapter_headings': True,
'max_toc_links': 50,
'minimum_line_height': 120.0,
'no_chapters_in_toc': False,
'no_default_epub_cover': False,
'no_inline_navbars': False,
'no_process': False,
'no_sort': False,
'no_svg_cover': False,
'output_format': u'png',
'output_profile': <calibre.customize.profiles.OutputProfile object at 0x05A2B1B0>,
'page_breaks_before': None,
'prefer_metadata_cover': True,
'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_0.7.44_tmp_hnewej\\calibre_0.7.44_yulifg.opf',
'remove_first_image': False,
'remove_paragraph_spacing': False,
'remove_paragraph_spacing_indent_size': 1.5,
'renumber_headings': True,
'replace_scene_breaks': u'',
'right2left': False,
'series': None,
'series_index': None,
'smarten_punctuation': False,
'sr1_replace': None,
'sr1_search': None,
'sr2_replace': None,
'sr2_search': None,
'sr3_replace': None,
'sr3_search': None,
'tags': None,
'timestamp': None,
'title': None,
'title_sort': None,
'toc_filter': None,
'toc_threshold': 6,
'unwrap_lines': True,
'use_auto_toc': False,
'verbose': 2,
'wide': False}
InputFormatPlugin: Comic Input running
on C:\Users\username\Calibre Library\Unknown\Herogasm 01 (883)\Herogasm 01 - Unknown.cbr
Python function terminated unexpectedly
C:\Users\username\Calibre Library\Unknown\Herogasm 01 (883)\Herogasm 01 - Unknown.cbr is not a RAR archive. (Error Code: 1)
Traceback (most recent call last):
File "site.py", line 103, in main
File "site.py", line 85, in run_entry_point
File "site-packages\calibre\utils\ipc\worker.py", line 110, in main
File "site-packages\calibre\gui2\convert\gui_conversion.py", line 31, in gui_convert_override
File "site-packages\calibre\gui2\convert\gui_conversion.py", line 25, in gui_convert
File "site-packages\calibre\ebooks\conversion\plumber.py", line 904, in run
File "site-packages\calibre\customize\conversion.py", line 204, in __call__
File "site-packages\calibre\ebooks\comic\input.py", line 410, in convert
File "site-packages\calibre\ebooks\comic\input.py", line 359, in get_pages
File "site-packages\calibre\ebooks\comic\input.py", line 24, in extract_comic
File "site-packages\calibre\__init__.py", line 191, in extract
File "site-packages\calibre\libunrar.py", line 179, in extract
calibre.libunrar.UnRARException: C:\Users\username\Calibre Library\Unknown\Herogasm 01 (883)\Herogasm 01 - Unknown.cbr is not a RAR archive.

[itimpi]

The message says that the cbr is not a valid rar file - any reason to believe that is not the case? Maybe for instance it is a zip file and should have the .cbz extension?