Permanent Reboot-Proof Solution

If you want a proper fix that survives reboots, follow these steps:

    Open a terminal.

    Create a new configuration file:

$ sudo nano /etc/modprobe.d/VBox-NoKVM.conf

    Paste the following content exactly into the file:

# This is so that VirtualBox can start.

# See:

# https://www.virtualbox.org/wiki/Changelog

#

# VirtualBox 7.1.4 (released October 15 2024)

# Linux Guest Additions: Introduce initial support for kernel 6.12 (NOTE:

# In kernel 6.12, KVM initializes virtualization on module loading by

# default. This prevents VirtualBox VMs from starting. In order to avoid

# this, either add "kvm.enable_virt_at_load=0" parameter into kernel

# command line or unload corresponding kvm_XXX module)

#

options kvm enable_virt_at_load=0

    Save the file and exit (in Nano, press CTRL+O, ENTER, then CTRL+X).

    Reboot your computer:

After the reboot, VirtualBox should now start your virtual machines without any issues.