VirtualBox - Ubuntu 18.04 LTS causing BSOD - AMD Ryzen 7 3750H

I am running an Asus GA502DU (AMD Ryzen 7 3750H (with Vega), Nvidia GeForce GTX 1660Ti MAX-Q, 16GB RAM(8+8), Intel NVMe SSD)

I just installed VirtualBox on Windows 10 64bit and started up Ubuntu 18.04 LTS giving it 4GB Ram and 1 core.

First time I laucnched it, I got a BSOD with a SYSTEM_SERVICE_EXCEPTION error code.

Second time I ran it - it worked perfectly until half way through the the setup when I was entering my desired username - no BSOD this time, the laptop just rebooted.

Third time I ran it, got through to desktop, opened terminal, firefox. Started installing updates and I got another BSOD - KMOD_EXCEPTION_NOT_HANDLED. Fourth time I ran it, it instantly gave me a BSOD with SYSTEM_SERVICE_EXCEPTION just like the first time.

What is going on?

Update:

It seems like Avast Antivirus was causing all that. There's a setting in there called "Hardware Virtualisation" - that needs to be disabled.

Haven't had a crash since.