When you want to copy/move from a shared folder (on Windows guests, for example) and it fails with absurd error messages (lots of text or an error about the target being read-only), you are probably running on Guest Additions that no longer match your VirtualBox version.

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Read more Show archive.org snapshot

Fix: install the latest VirtualBox Guest Additions in your guest machine.

Note that you need to make sure you are using the correct ISO.