If your Event Viewer Log says "The VirtualBox system service service terminated unexpectedly" with Event ID 7034, follow ...
If VirtualBox stuck on Saving state, your machine is in the hung state. Kill the VM via the Command Prompt, disable Core ...
If you need to use virtual machines on Linux, try Virt-Manager. Virt-Manager is more reliable than VirtualBox. Virt-Manager is completely free and open-source. I'm a long-time supporter of VirtualBox.