ACPI autoload failed: no such file or directory

since several days;  i ' got this message before the kernel load (not 
easy to see that, is not include in the logs)

ACPI autoload failed: no such file or directory

after the boot process, i logged in and try this command

#kldload acpi.ko
kldload: can't load usb.ko: No such file or directory

#kldload /boot/kernel/acpi.ko
in this case the system try to load the module and, of course,  it can't.


- the acpi.ko file is present in /boot/kernel
- i didn't changed anything ,  except  a fresh  kernel build
- kldload works with other modules in this directory.


anyone could explain this.. strange thing?

nota : the system  boot and work perfectly. Only the ACPI functions are 
absent.. (it isn't a big problem for me, but i whish understand)