Recently moved to XS 8.2 on new hardware - seen a couple of FreeBSD DomU lock ups?

Hi all,

We've been running FreeBSD as a DomU under Xen Server for years now, and 
only really had a few now 'known' issues (e.g. with networking).

We've recently setup XS 8.2 on some new Dell servers, and whilst everything 
appears fine - twice now in a couple of weeks we've had FreeBSD DomU's just 
"lock up".

There's no errors logged, no kernel panic, nothing - they just "stop". Xen 
reckons the CPU is pegged at 100% (with brief periods of zero) - the 
console is still 'available' (but locked up) - and the kernel is dead (i.e. 
you cannot ping it).

Aside from the "Has anyone else seen similar" - with nothing in the logs, 
no panic, nothing - I'm kind of at a loss as to how best to troubleshoot 
this further?

The VM's are lightly loaded - haven't run out of resources (RAM /CPU etc.) 
- and it's only happened a couple of times now (but in a couple of weeks) - 
whereas our setup before never experienced this in it's lifetime.

One was a legacy 11.4 system (amd64) - the other was a 12.3 system (amd64).

A forced reboot brings them back (with some file system damage - as you'd 
expect from a crash).

Just at a loss as to where to look - given the lack of any panic/errors 
etc. Any suggestions?

Regards,

-Karl