Hi,
When I tried to use VirtualBox all my images failed to load and a popup appeared showing NS_ERROR_FAILURE (0x80004005). In the forum one can find several solutions for the problem, however the one that worked for me was:
What I noticed is that my extension was 6.1.36, but VB was 6.1.34, so I downloaded the correct extension from here:
https://download.virtualbox.org/virtualbox/6.1.34/Oracle_VM_VirtualBox_Extension_Pack-6.1.34.vbox-extpack
After loading VB as root and manually installing it, everything worked fine again.
Cheers