weird message freezing kb at bootup

[hd77]

hello

when booting on my openbsd, I have the following one :

acpitz1: critical temperature excedded 3427C, shutting down

problems are :
* laptop is not especially hot, room temperature is a bit cold so..
* kb is doing absolutely nothing, it appears just seconds before the /home enciphered password is asked, blocking me to enter it
* its a loopback message, can stop it only by salvage poweroff..

how could I manage it?
I thank you vm