Hi again,

contrarily to what I stated in my last message, I found a way to wake up 
my laptop without hitting the power key (in fact any "BIOS" key works). 
But the effect is almost as deceiving as before: the laptop does not 
wake up, it rather reboots as if it had been powered up.

Here is the dmesg before and after:

acpi0: entering state 3
ath0: ath_cardbus_power
pckbd0: suspending...
pckbport: command timeout
pckbport_cmd: send error
pckbd_disable: command error
pckbc_slot_enable(0) failed
acpi0: good morning!
Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 
2005, 2006
     The NetBSD Foundation, Inc.  All rights reserved.
Copyright (c) 1982, 1986, 1989, 1991, 1993
     The Regents of the University of California.  All rights reserved.

NetBSD 3.99.21 (PRESARIO) #0: Thu Jun 22 09:13:28 CEST 2006
         vincent@vincent:/sys/arch/i386/compile/PRESARIO
total memory = 767 MB
[etc.]

Vincent