troubleshooting linuxcnc realtime under virtual box emulation

Hi !
i'm getting a segmentation fault error trying to initialize LCNC under VBox emulation. both under Debian and under Ubuntu machines.
This is quite strange because im cloning both virtual machines that worked ok in a similar Pc (same mother, processor and OS).
also created a new one and same problem...
make me think about a config issue in the host PC (which is running Windows 7 64)
I checked for lapic in the machines bootloaders and they are set ok...

when i ran realtime start, i get a segmentation fault error (issued by insmod trying to insert rtai_hal.ko)

if i issue realtime start for a second time i get the message rtai_hal.ko is already loaded

strangely lsmod list it as installed but rmmod cant remove it because it says is in use.

don't know how to continue...
any help is highly appreciated

can't find any other additional info to get more ideas of what else / where can i check...

Hi Andy. thnks for your reply.

reboot dont help. same results
my best guess is that the problem could be on the Windows host config and/or the VirtualBox config.

because the VMs I ran worked ok on another similar PC

I also tried to boot many live isos (1st img) with same results...

quite strange the highlighted msg (2nd snapshot)

any clues ?

Hi guys, finally i've found the problem . Apparently there's no room for nested pagination... Disabling solved the problem (attached pic). Now i have all my LCNC emuls running again !!! Happy International Workers' Day !!