Fatal trap 12: page fault while in kernel mode - unable to trace

Not sure if this is the correct forum, if not then please move my message....

I've been happily running pfSense for several months without incident but had to reboot a few days ago and have been unable to do so as the system traps on bootup.

I get
Fatal trap 12: page fault while in kernel mode

followed by various pointer addresses and eventually a db> prompt where apparently I should type in trace. Unfortunately the system is unresponsive at this point..

Before the trap msg appears there is something about setting
in /boot/loader.conf and then
random: <Software, Yarrow> initialized
Just before the db> prompt it says
Stopped at     vesa_configure+0xbb9:   movl  $0xffffffff,(%rcx,%rax,1)

Can anyone tell me if this is a hardware fault, either memory or disk - I have 100GB Intel SSD...

I have manged to managed to boot FreeBSD 10.1 from an external disk so am able to carry out diagnostics on the system if necessary but not sure what to look for... Is there a memory test program available to FreeBSD?
How do I check the SSD disk? I can't seem to mount it and not sure how to fsck it. I did see a post showing how to check for bad sectors using dd but can't remember the parameters...