I am also seeing this error, on a just-purchased EPIA M840 (1.2 GHz VIA Nano).
I can reproduce the errors by loading the CPU, RAM, and I/O eg with a buildkernel or buildworld with -j3.
I've tried the board now under 8.1 and 8.2-RC, both amd64 and i386. Running amd64 the errors seem to occur more frequently, under i386 less.
I have also tried varying most BIOS options that seem conceivably related, but these EPIA machines don't have many options.
Naturally I can suppress the messages by disabling APIC on i386. Amd64 failed to boot without APIC. However, disabling APIC on such a recent machine would seem to have significant performance/efficiency consequences, so I hope the problem can be resolved otherwise.
I have checked, and VIA offers no newer BIOS for this machine.
I'm unsure if it's related, but this machine has also exhibited an unusual network problem. It has two vge PCIe interfaces. When the machine is acting as a PPPoE client with pf and NAT, client TCP sessions to certain servers will fail to establish, and time out, much like the behavior I would expect with path MTU discovery problems. With the affected services, the problem is 100% repeatable.
However, when I move the same disk to an Opteron laptop, changing *only* the interface names in rc.conf, pf.conf, and ppp.conf, the gateway setup works flawlessly.
I would be happy to run instrumented debug kernels, obtain vmcore dumps, etc. I recently gained a fair bit of experience collecting such data working on an unrelated issue.