[SmiLynnLady]

I got two error messages as I was cleaning up Author(s) info. in Calibre.
So I closed Calibre - opened it up again expecting things to have cleared up - and suddenly I have ZERO BOOKS in Calibre. (My "Calibre Library" file with over 4,000 books appears to be okay. I copied it elsewhere to keep it from being damaged while I try to fix things.)

What do these error messages mean? Did I do something to cause the problem?

ERROR MESSAGE 1
calibre, version 0.8.9
ERROR: Unhandled exception: <b>DatabaseException</b>:disk I/O error
RemoteTraceback (most recent call last):
File "site-packages/calibre/library/sqlite.py", line 268, in run
OperationalError: disk I/O error
Traceback (most recent call last):
File "site-packages/calibre/gui2/library/models.py", line 889, in setData
File "site-packages/calibre/library/database2.py", line 1929, in set
File "site-packages/calibre/library/database2.py", line 2189, in set_authors
File "site-packages/calibre/library/database2.py", line 2133, in _set_authors
File "site-packages/calibre/library/sqlite.py", line 308, in run
DatabaseException: disk I/O error
RemoteTraceback (most recent call last):
File "site-packages/calibre/library/sqlite.py", line 268, in run
OperationalError: disk I/O error
-------------------
ERROR MESSAGE 2
calibre, version 0.8.9
ERROR: Unhandled exception: <b>DatabaseException</b>:disk I/O error
RemoteTraceback (most recent call last):
File "site-packages/calibre/library/sqlite.py", line 268, in run
OperationalError: disk I/O error

Traceback (most recent call last):
File "site-packages/calibre/gui2/ui.py", line 692, in closeEvent
File "site-packages/calibre/gui2/ui.py", line 602, in write_settings
File "site-packages/calibre/gui2/init.py", line 278, in save_layout_state
File "site-packages/calibre/gui2/library/views.py", line 331, in save_state
File "site-packages/calibre/gui2/library/views.py", line 325, in write_state
File "site-packages/calibre/library/prefs.py", line 58, in set
File "site-packages/calibre/library/prefs.py", line 53, in __setitem__
File "site-packages/calibre/library/sqlite.py", line 308, in run
DatabaseException: disk I/O error
RemoteTraceback (most recent call last):
File "site-packages/calibre/library/sqlite.py", line 268, in run
OperationalError: disk I/O error
-----------------------
Can you tell me what happened, and how to keep it from happening again? Can I just download Calibre again and tell it to use the same "Calibre Library" - or do you think the Library itself is damaged?