Limitations of VirtualBox 4.3.16_ose on FreeBSD 10.1-RELEASE

[rondzierwa at comcast.net]

I am trying to build a ubuntu14.04 guest on FreeBSD 10.1 using Vbox 4.3.16_OSE. It seems that it will not boot reliably if I allocate more than 2 cpu's. When I set the cpu count to 4, sometimes it does not start at all, but freezes during boot (the ubuntu screen with the rotating dots). 
I have booted it with 2 processors, and installed vbox tools, but still, when I increase the number of cpu's past 2 it will not boot. 

any ideas?