[Magnus]

Added new books. After downloading metadata and selecting cover I either click OK to exit metadata, or I click the forward arrow to move onto the next book to add metadata.

When I do this often Calibre pops-up an error window ...

calibre, version 2.77.0
ERROR: Unhandled exception: error: (32, 'DeleteFile', 'The process cannot access the file because it is being used by another process.')

calibre 2.77 [64bit] embedded-python: True is64bit: True
Windows-8-6.2.9200 Windows ('64bit', 'WindowsPE')
('Windows', '8', '6.2.9200')
Python 2.7.9
Windows: ('8', '6.2.9200', '', 'Multiprocessor Free')
Successfully initialized third party plugins: DeDRM (6, 3, 6) && K4PC, K4Mac, Kindle Mobi and Topaz DeDRM (0, 4, 2) && Inept Epub DeDRM (0, 1, 7) && Inept PDF DeDRM (0, 1, 4) && Ignoble Epub DeDRM (0, 1, 6) && eReader PDB 2 PML (0, 0, 6)
Traceback (most recent call last):
File "site-packages\calibre\gui2\metadata\single.py", line 622, in next_clicked
File "site-packages\calibre\gui2\metadata\single.py", line 554, in apply_changes
File "site-packages\calibre\gui2\metadata\basic_widgets.py", line 219, in commit
File "site-packages\calibre\db\legacy.py", line 816, in func
File "site-packages\calibre\db\cache.py", line 61, in call_func_with_lock
File "site-packages\calibre\db\cache.py", line 1074, in set_field
File "site-packages\calibre\db\cache.py", line 1088, in update_path
File "site-packages\calibre\db\backend.py", line 1566, in update_path
File "site-packages\calibre\utils\filenames.py", line 461, in delete_originals
error: (32, 'DeleteFile', 'The process cannot access the file because it is being used by another process.')

Any ideas? Usually clicking OK or forward error again allows Calibre to move on.