VirtualBox error “VT-x is disabled in the BIOS. (VERR_VMX_MSR_VMXON_DISABLED)”

After updating my Fedora 19 x64 I tried to open a VM I have installed on it but received this error:

VT-x is disabled in the BIOS. (VERR_VMX_MSR_VMXON_DISABLED)

It is supposed that I had to enable some VT-x configuration in the BIOS, but I’ve never touch the configuration before or after the update, so that couldn’t be the problem.
The current VirtualBox version installed is 4.3.4 and kernel is 3.11.10.

If you are in the same situation as me (you can’t change or you don’t want to change the BIOS config), what you can do is touch the VM. First, get the name and UUID of the VM you want to fix:

VBoxManage list vms
"My Guest VM Name" {e6b08efd-0453-497b-b934-ff8ad17baad3}

This gives you the VM’s name and UUID. Then turn off the long mode flag:

VBoxManage modifyvm "My Guest VM Name" --longmode off

Tha bad side of this is that I don’t know why it got broken after the update, the good thing is that I can continue working.