VirtualBox VT-x virtualization stopped working

Question

virtual box

Virtualbox has disabled support for virtualization, no machine starts. Before that, everything worked, the processor supports virtualization and the option is activated in the BIOS.
What is the reason?
Could this be due to the Vagrant installation (it works with VirtualBox)?
Win 8.1, VirtualBox 4.3.6 r91406.

Не удалось открыть сессию для виртуальной машины ubuntu.

VT-x is not available. (VERR_VMX_NO_VMX).

Код ошибки: E_FAIL (0x80004005)
Компонент: Console
Интерфейс: IConsole {8ab7c520-2442-4b66-8d74-4ff1e195d2b6}

Answer 1

My OS does not start on a virtual machine when the BlueStacks App Player agent is active.
This player also uses virtualization to run android applications.
Try to close something and run again.

Answer 2

Thanks for the answer. BlueStacks App Player is also available, but Hyper-V interfered in my case. The removal from the components of Windows helped.