I had a siimilar issue recently for an unrelated project. A little googling at the time turned up a few things to check...this doesn't appear to be a SAS-only concern.
Your Host OS is 64-bits (obviously is)
Check that Intel Virtualization Technology and VT-d are both enabled in the BIOS.
Ensure that he Hyper-V platform is disabled in your Windows Feature list.
If these don't help, you may want to check the Virtualbox forums to see if others fixed it.
=G=