The thread promises a fix. Until that happens I've done a workaround:
a. As root:
i. Move the following to a user directory, e.g.,
ii. Link them back to /root, test: Yes, it still works for root.
iii. Recursively change permissions to your non-root user, e.g., andy:users
iv. Test: Yes, it still works for root.
However N.B.: having opened them as root the vbox and log files are saved with now root permissions!
You'll have to change them back to andy:users.
b. As andy:
i. Link them back to /home/andy
ii. Edit VirtualBox.xml
iii. Test: Now it works for andy.