Calibre database access issues

I'm having database access issues for a number of tasks in Calibre - the output from a simple move book between libraries is given below. I'm getting these issues on both a full install of Calibre plus a portable install on a work laptop that I do not have full admin rights on so wondering if this is related?

calibre, version 2.76.0
ERROR: Failed to copy books: Could not copy any books, click "Show Details" for more information.

Failed to copy a book, see below for details

Copying: Bone failed, with error:
Traceback (most recent call last):
File "site-packages\calibre\gui2\actions\copy_to_library.py", line 156, in _doit
File "site-packages\calibre\gui2\actions\copy_to_library.py", line 194, in do_one
File "site-packages\calibre\db\legacy.py", line 246, in import_book
File "site-packages\calibre\db\cache.py", line 1569, in add_books
File "site-packages\calibre\db\cache.py", line 61, in call_func_with_lock
File "site-packages\calibre\db\cache.py", line 1539, in create_book_entry
File "site-packages\calibre\db\cache.py", line 1261, in set_metadata
File "site-packages\calibre\db\cache.py", line 1088, in update_path
File "site-packages\calibre\db\backend.py", line 1551, in update_path
File "site-packages\calibre\db\tables.py", line 135, in set_path
File "site-packages\calibre\db\backend.py", line 822, in execute
File "c:\cygwin64\home\kovid\sw\build\apsw-3.8.2-r1\src\cursor.c", line 231, in resetcursor
CantOpenError: CantOpenError: unable to open database file