Win10 cannot be started on my iMac

[wolfilein]

Suddenly VirtualBox (5.2.16) gives the following error message:
"Cannot attach medium '/Applications/VirtualBox.app/Contents/MacOS/VBoxGuestAdditions.iso' {b61b54f3-34d8-47cf-b871-b16b861b5e7b}: medium is already associated with the current state of machine uuid {51667249-a0c0-4c2b-8871-3cdb64a6cd1e}!.
Fehlercode:
VBOX_E_OBJECT_IN_USE (0x80BB000C)
Komponente:
MediumWrap
Interface:
IMedium {4afe423b-43e0-e9d0-82e8-ceb307940dda}"
Yesterday there was a major update of Win10, probably this has caused this error message in VirtualBox. My iMac has the actual version of MacOS.
There was no change after downloading the latest version 5.2.18 of VirtualBox. Looking at the VBoxGuestadditions.iso, it says that it is from August 14, so it appears it is still the old version, probably should be updated to the actual version 5.2.18, but no idea how to do this and if this would help?
Any ideas?

[socratis]

medium is already associated with the current state of machine

You have a saved state, in which you had mounted a previous version of the VBoxGuestAdditions.iso. Each different version has a different UUID, hence the conflict. You need to remove that saved state. You have two options:

1. Downgrade to the VirtualBox version that you had before, restore that saved state, eject the CD, shutdown the VM, and then upgrade VirtualBox. Or
2. Remove that saved state.

[wolfilein]

"Remove that saved state", what exactly must I do ???

[socratis]

You should either have the VM in a saved state, in which case you have to click on the top 2nd button from the left labelled "Discard" (not Remove, sorry), or if you have a snapshot (which includes the VBoxGuestAdditions.iso) remove that snapshot.

Can you right-click on the VM in VirtualBox Manager, select "Show in Finder", "Compress" that .vbox file and attach it here? See the "Upload attachment" tab below the reply form.

[wolfilein]

On my VM I can only click on the first button, which is "new", the rest is grey and cannot be clicked on, right-clicking on the VM does not lead to "show in finder", and I do not have any snapshots, so what else can be done ???

I can click on "global tools" and clicking on "optical media" the VBoxguestadditions.iso appears and I could click on remove or move, but probably I should not do this ??

[socratis]

right-clicking on the VM does not lead to "show in finder"

Try it again. What does the menu say when you right-click on the VM?

[wolfilein]

Right clicking on the VM gives: "show toolbar, show toolbar-text, show status line", that is all

[socratis]

You are clicking on the splitter bar. Try to click on the VM icon, a little bit to the left...

[wolfilein]

Clicking on the symbol gives "remove, update, sort" as clickable items, the other menu items are grey and not clickable.
But I could solve the problem by adding the VM from my external backup harddisk and cloning it, and removing the old not working VM, so now everything is working as before.
Thanks for your help.