It would be safer to not upgrade freebsd-image to version 7.2-5 on kfreebsd-i386. There is a kernel panic during startup. All the flavours (486 and 686) are affected by this bug.
I just tried 486 and 686 flavours under QEMU, they both boot fine. Could you also try to boot without acpi ? Does 7.2-4 boot for you ? The most important difference would be different compiler used to compile them. Petr