id	summary	reporter	owner	description	type	status	component	version	resolution	keywords	cc	guest	host
13776	Failed to open a session for the virtual machine vm. VT-x is not available.	KenD		"I'm running Windows 8.1, with Intel Core i5-3570K cpu, Gigabyte Z77X-UD3H motherboard, and Virtual Box 4.3.20. The bios is set to enable virtualization. Using Intel's Processor Identification Utility, I've verified ""Intel(R) Virtualization Technology"" is ""Yes"", meaning it's enabled. In VirtualBox 4.3.20, all virtual machines do not start: ""VT-x is not available"". Rolling back to VirtualBox 4.3.18, all virtual machines work fine. Identification of the virtualization state no longer works for my machine.

In addition, I've noticed that VirtualBox---somehow---altered the settings of the virtual machine, specifically the number of processors. It really should never change my settings without my permission."	defect	closed	other	VirtualBox 4.3.20	invalid			Windows	Windows