r320358 panics immediately on boot / AMD64-GENERIC kernel

[Michael Jung]

After upgrading from 318959 to 320358 I immediately get the attached 
panic.

This is AMD64 / GENERIC kernel.

/boot/loader.conf is empty.

The system boots off a UFS2 partition.

This is a virtual guest and I do currently have a serial cable.

Short of figuring out how to virtualize a serial console from a ESXi 
guest is
there any more information I can provide?

Thanks.

Mike