Virtualbox periodically "Loses" vboxflt and vboxusb drivers after host reboot

[texneus]

After creating a crossbow virtual network adapter "vnic0" in the host OS, and creating an Ubuntu VM (in this case) named "Sub-Etha" with a bridged network adapter (bridged to the crossbow vnic0), the host intermittently will lose the subject drivers when the host is rebooted (using "shutdown -i6 -g0" from a command line) or is power cycled (using "shutdown -i5 -g0" from a command line). When the drivers are lost, Virtualbox will open as usual but attempting to start the Ubuntu VM results in the Virtualbox displaying the following error in a window after very briefly flashing the BIOS screen:

Failed to open session for the virtual machine Sub-Etha

Failed to open/create the internal network
'HostInterfaceNetworking-vnic0'
(VERR_SUPDRV_COMPONENT_NOT_FOUND).

Failed to attach the network LUN
(VERR_SUPDRV_COMPONENT_NOT_FOUND).

When this occurs, the vbox drivers can be verified as being missing:

# modinfo | grep -i vbox
170 fffffffff7b5a590    ce8 292   1  vboxnet (VirtualBox NetAdp 4.2.10r84104)
172 fffffffff80c9000  34ee0 291   1  vboxdrv (VirtualBox HostDrv 4.2.10r84104)
212 fffffffff7dc1dd8   4580 294   1  vboxusbmon (VirtualBox USBMon 4.2.10r84104)

The drivers can be re-installed as follows:

(shutdown Virtualbox)
# rem_drv vboxflt
# add_drv vboxflt

The drivers can be verified to be re-installed using the first command above:

# modinfo | grep -i vbox
170 fffffffff7b5a590    ce8 292   1  vboxnet (VirtualBox NetAdp 4.2.10r84104)
172 fffffffff80c9000  34ee0 291   1  vboxdrv (VirtualBox HostDrv 4.2.10r84104)
212 fffffffff7dc1dd8   4580 294   1  vboxusbmon (VirtualBox USBMon 4.2.10r84104)
219 fffffffff7dd8a80   7510 293   1  vboxflt (VirtualBox NetDrv 4.2.10r84104)
219 fffffffff7dd8a80   7510   -   1  vboxflt (VirtualBox NetMod 4.2.10r84104)
255 fffffffff8129000   7478 295   1  vboxusb (VirtualBox USB 4.2.10r84104)

(note the addition of the final three lines, 2 relating to vboxflt and 1 relating to vboxusb). The VM will now operate normally. However, the drivers will disappear again after an indeterminant number of host reboots, but is believed to be 10 or less.

NOTE1: This problem and above workaround is also documented in forum thread ​https://forums.virtualbox.org/viewtopic.php?f=11&t=40509 and dates to at least 2011 with Virtualbox 4.0.4. I could not find an existing bug report for this problem.

NOTE2: Host OS is Openindiana 151a7, however above thread shows issue has also occurred in Sun/Oracle Solaris hosts.

NOTE3: Virtualbox Extension Pack is not installed as it is not required for my VM.

NOTE4: The effect or symptoms of the lost USB driver is unknown - I'm not using any USB devices in the VM, but all three drivers are affected regardless.

NOTE5: Screenshot of error and log files attached.

[texneus]

Virtualbox error screen grab

[texneus]

Virtualbox logs

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.