Linux guest VM system hangs and crash under VirtualBox 4.3

There is currently a bug under VirtualBox 4.3 when using the most recent 64-bit linux kernels such as on CentOS 6.4 (kernel 2.6.32-431.el6.x86_64).

If you try to downgrade to 4.1, you will have trouble installing guest additions. However with VirtualBox 4.2.20, you will have stability and be able to install VirtualBox guest additions !

VirtualBox 4.1 => Not ok (Guest additions kernel header failure)
VirtualBox 4.2 => OK
VirtualBox 4.3 => Not ok (VT-x code bug)

<< It is my understanding that the VT-x code was heavily reworked in the 4.3 release, so that may be part of the problem. >> -- https://forums.virtualbox.org/viewtopic.php?f=7&t=57842