Unknown Book Type error v0.9.44

[aegisrose]

Hello Calibre Forum,
I was just wondering whether this is corrupt, or if it's something I can salvage... I don't want to go changing extensions, or try to convert without a little guidance.

calibre, version 0.9.44
ERROR: Could not open ebook: Unknown book type: '\x00\x00\x00\x00\x00\x00\x00\x00'

Traceback (most recent call last):
File "site-packages\calibre\gui2\viewer\main.py", line 40, in run
File "threading.py", line 763, in run
File "site-packages\calibre\ebooks\oeb\iterator\book.py", line 99, in __enter__
File "site-packages\calibre\customize\conversion.py", line 241, in __call__
File "site-packages\calibre\ebooks\conversion\plugins\mobi_in put.py", line 32, in convert
File "site-packages\calibre\ebooks\mobi\reader\mobi6.py", line 83, in __init__
MobiError: Unknown book type: '\x00\x00\x00\x00\x00\x00\x00\x00'

Thanks in advance,
aegis