Cansado de ver as mensagens surgindo o tempo todo:

acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C) 
acpi_tz0: _CRT value is absurd, ignored (256.0C)

Fiz uma alteração nessa parte do ACPI e removi a mensagem. Acho que não vai fazer muita falta mesmo... 

--- /usr/src/sys/dev/acpica/acpi_thermal.c-original 2008-06-08 17:38:40.000000000 -0300 
+++ /usr/src/sys/dev/acpica/acpi_thermal.c 2008-06-08 17:39:27.000000000 -0300 
@@ -677,8 +677,10 @@ 
acpi_tz_sanity(struct acpi_tz_softc *sc, int *val, char *what) {
 if (*val != -1 && (*val < TZ_ZEROC || *val > TZ_ZEROC + 2000)) {
   + /* device_printf(sc->tz_dev, 
   "%s value is absurd, ignored (%d.%dC)\n", 
   what, TZ_KELVTOC(*val)); 
+ */ *val = -1;
 } 
}