1) maybe this a virtualbox bug, could you please try with vmware player, download link in this thread : [You must be registered and logged in to see this link.]
2) b) try to don't integrate this window update "KB2811660" (Information link : [You must be registered and logged in to see this link.])
2) b) try to don't integrate this window update "KB2811660" (Information link : [You must be registered and logged in to see this link.])