so following the procedure here
https://unix.stackexchange.com/questions/52951/gedit-wont-save-a-file-on-a-virtualbox-share-text-file-busy
What fixed it for me (still a bit annoying but works), and is applicable to gedit, is to:
edit - preferences - editor Put a check on "Create backup copy"
When saving from now on, save the file once, ignore the error, save again. works every time.
