VM fails to start with error: VERR_VMX_IN_VMX_ROOT_MODE

[DocBrown]

I am running a distributed computing app BOINC running a project called VirtualLHC@home. This app launches a Linux26 VM guest. This guest will fail to start with the following error logged:

00:00:01.850366 HM: Failed to initialize VT-x / AMD-V: VERR_VMX_IN_VMX_ROOT_MODE
00:00:01.850403 HM: VMX MSR_IA32_FEATURE_CONTROL=5
00:00:01.850420 VMSetError: D:\tinderbox\win-4.3\src\VBox\VMM\VMMR3\HM.cpp(914) int __cdecl hmR3InitFinalizeR0(struct VM *); rc=VERR_VMX_IN_VMX_ROOT_MODE
00:00:01.850424 VMSetError: VT-x is being used by another hypervisor.

I think I have narrowed the problem down to my recent installation of BitDefender Internet Security. When I disable the startup of BD, the VM launches correctly. Also If a launch another Windows XP VM, prior to the launch of the VirtualLHC@home project the vm starts correctly.

I am working with BD support, but I am posting here in the hopes I can get some detail about how to locate what resource BD running that is preventing the VM from starting or if possible how to prevent this. I'm not confident that BD support will be willing to go the extra mile to find this.

I am running:
Host: Windows 7 x64 SP1
VB: VirtualBox VM 4.3.12 r93733 win.amd64 (May 16 2014 13:57:11)
Oracle VM VirtualBox Extension Pack (Version: 4.3.12 r93733; VRDE Module: VBoxVRDP)
Guest OS type: 'Linux26'

I have attached the vm log file containing the error.

I would appreciate any information that would help me locate the problem.

Good day,
John

[mpack]

You have VT-x enabled in the VM settings, meaning VT-x is required to run this VM. But, something else is already using it - I can't tell you what.