(Jaunty) suspend fails if battery saving script is in /etc/pm/sleep.d/

[Lele83x]

If there's battery saving script putted in /etc/pm/sleep.d that includes a line such as:

echo 6 > /sys/bus/pci/drivers/iwl3945/0000:03:00.0/power_level

the notebook fails to suspend on Jaunty

the message in pm-suspend.log is:

/etc/pm/sleep.d/90-save_power.sh suspend suspend: /etc/pm/sleep.d/90-save_power.sh: line 16: echo: write error: Resource temporarily unavailable
Returned exit code 1.

where line 16 is exactly:

echo 6 > /sys/bus/pci/drivers/iwl3945/0000:03:00.0/power_level

the notebook suspended fine on Intrepid with the same script.

What other infos should I include ?

Thanks