Windows – VT-x is enabled, but it’s not detected as such

I preemptively reinstalled Windows 7 Ultimate x64 recently, but I lost the ability to use VT-x in the process. Namely, I was trying to get HAXM to work, but I will surely need it later for VirtualBox. It's enabled in the BIOS, but several programs detect it as available, but disabled.

Before this, VirtualBox worked normally and, since the first time that I ran a virtual Android device, HAXM was installed and running without needing a dedicated installation. My hardware didn't changed between VT-x working and not working.

Here's what I got after some searching:

I tested with NX bit enabled and disabled.

I tested disabling VT-x, restarting, enabling it starting again.

I removed "Tablet PC Components" from Windows Features.

Avast's "Enable hardware-assisted virtualization" is checked.

None of these made VT-x work again. Both HAXM's installation and Microsoft's HAV Detection Tool say VT-x is available but disabled. I have no other virtualization technology installed. Also, just for curiosity, I made a test on Xubuntu 14.04. Running rdmsr 0x3A returns 5.

CPU: Intel Core i3-2100

Motherboard: Gigabyte H61M-S1

So, what do I have to do to make VT-x work again?

Thanks in advance.