freebsd stable - Nov 2007 - 6.3-BETA1: acpi_tz0: _TMP value is absurd, ignored (-13.4C)

I upgraded an old machine from 6.2-RELEASE-p7 to 6.3-BETA1 (via 
freebsd-update).

Now every ten seconds I get:

acpi_tz0: _TMP value is absurd, ignored (-13.4C)

At the same time, I have:

hw.acpi.thermal.tz0.temperature: -273.2C

The machine has a Gigabyte GA-686BX board with Intel 82440 BX chipset 
(nine years old).

I do not know what the temperature was on 6.2, but I did not get the 
dmesg output. If that is interesting, I could rollback the upgrade.

Anything I can do but setting hw.acpi.thermal.polling_rate to 0?

Thanks,
Jan Henrik