VirtualBox Suddenly Stopped Working...

[snoopx]

Several months ago I installed VirtualBox 6.1 on Win 7 Ultimate x64 and initially it worked. I was able to install both Win 7 Ultimate x64 and Win 10 Home as guests.
However, these last few days it's stopped working.
On trying to start it, I get the message:
"VirtualBox - Guru Meditation
A critical error has occurred while running the machine and the machine execution has been stopped..."
Attached are VBox.log and VBox.png as requested in the error message.
Curiously, I also have Windows XP Mode in Windows Virtual PC installed which has also stopped working, with the error message: "Cannot start Windows Virtual PC while another virtualisation software is running. Please close the other virtualisation software and try again". I have checked in Task Manager and cannot see any components of VirtualBox running so don't know what it is referring to. I don't know if the problems with both virtualisation softwares are connected.
Thanks in advance for any help or ideas on trying to fix this.

Host Computer Hardware:
Asus P5B
Intel Core 2 Quad Q6600 @ 2.4GHz Processor
8GB RAM

[mpack]

Disable the hardware virtualization option in your AVG or Avast settings. Then reboot the PC.

[snoopx]

Thanks for the prompt reply mpack. You're a genius. That seems to have fixed both virtualisation softwares!