APM: The system doesn't standby or suspend

[Marci]

Hi all, when I try to put the system in standby mode or suspend mode by 
APM with the command apm -s or apm -S in the console I see the HDs that 
powers off , and the monitor powers off too, but after few seconds the 
system awakes automatically from the suspend mode (or standby) .

I use the kernel 2.4.21-pre6 on an MSI KT4 Ultra + Athlon XP 2400+

Thanks for help

Bye