Problem with Vbox after recent upgrade

FreeBSD FBSD10 10.0-CURRENT FreeBSD 10.0-CURRENT #26 r238626: Thu Jul 19 
17:07:52 EDT 2012     root_at_FBSD10:/usr/obj/usr/src/sys/MYKERNEL  amd64

After a recent upgrade, when I try to start a VM it fails with:
Failed to open a session for the virtual machine OpenSuse11.4.

The virtual machine 'OpenSuse11.4' has terminated unexpectedly during startup 
with exit code 1.

Result Code: NS_ERROR_FAILURE (0x80004005)
Component: Machine
Interface: IMachine {5eaa9319-62fc-4b0a-843c-0cb1940f8a91}

Kernel driver not installed(rc=-1908)
Make sure the kernel module has been loading successfully

If I try to load vboxdrv.ko  manually I get:

# kldload vboxdrv.ko
kldload: can't load vboxdrv.ko: Exec format error

# kldstat
Id Refs Address            Size     Name
  1   16 0xffffffff80200000 d0deb8   kernel
  2    1 0xffffffff80f0e000 10ae520  nvidia.ko
  3    3 0xffffffff81fbd000 48558    linux.ko
  4    1 0xffffffff82212000 3df6     linprocfs.ko


# cat /boot/loader.conf
loader_logo=beastie
nvidia_load="YES"
vboxdrv_load="YES"

# Boot-time kernel tuning
kern.ipc.shmseg=1024
kern.ipc.shmmni=1024
kern.maxproc=10000

Vbox had been running fine before the upgrade.

I recently built world with the following for the first time:
# cat /etc/src.conf
WITH_BSDCONFIG=YES
WITH_BSD_GREP=YES

could this affect vbox?

# dmesg |grep vbox
KLD file vboxdrv.ko - could not finalize loading

Apparently the vbox kernel module is failing to load.

Any help is appreciated.