Problem
While on the Mac, trying to save a file to the network share, you get an error message saying, 'File in Use', even though you do not have the file opened in any way.
Cause
This is a known bug with Mac OS X with Samba File shares with regards to Icon Preview enabled on both the source folder and the destination folder. It appears that Mac OS X maybe not closing the file properly when it generates the Icon Preview.
Noted from Apple's Forums: Strange Problem when Copying files to NAS
Solution
It is recommended that on the properties of both the folder you are copying a file from and the folder you are copying to on the Mac to have 'Show Icons' unchecked.
The instructions on how to disable this is listed here: How to Disable Finder Icon Thumbnails and Previews for Images & Video Files
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