MA311 refuses to set txpower

[Paolo]

Hi!

I just mounted a MA311 Netgear card and flashed with a newer firmware.
Now i have:

Downloading to volatile memory (RAM).
OK.
Components after download:
  NICID: 0x8013 v1.0.0
  PRIID: 0x0015 v1.1.4
  STAID: 0x001f v1.8.2

(these are volatile firmwares, i also updated the non volatile firmwares
to 1.1.1 and 1.8.2 respectively, cause i couldnt find a non volatile
version of 1.1.4 which suited my card).

Ok, anyways, i would like to set txpower of my card (to lower it).
it works fine if i do 

# iwconfig wlan0 txpower off

but if i do try to set it, i geterrors like:

root at rivendell:/local/soft/Hardware/WiFi/Prism2# iwconfig  wlan0
txpower 3
Error for wireless request "Set Tx Power" (8B26) :
    SET failed on device wlan0 ; Operation not supported.
root at rivendell:/local/soft/Hardware/WiFi/Prism2# iwconfig  wlan0
txpower 15mW
Error for wireless request "Set Tx Power" (8B26) :
    SET failed on device wlan0 ; Operation not supported.
root at rivendell:/local/soft/Hardware/WiFi/Prism2# iwconfig  wlan0
txpower 30
Error for wireless request "Set Tx Power" (8B26) :
    SET failed on device wlan0 ; Operation not supported.
root at rivendell:/local/soft/Hardware/WiFi/Prism2# iwconfig  wlan0
txpower 1
Error for wireless request "Set Tx Power" (8B26) :
    SET failed on device wlan0 ; Operation not supported.
root at rivendell:/local/soft/Hardware/WiFi/Prism2# iwconfig  wlan0
txpower 10
Error for wireless request "Set Tx Power" (8B26) :
    SET failed on device wlan0 ; Operation not supported.
root at rivendell:/local/soft/Hardware/WiFi/Prism2# iwconfig  wlan0
txpower 4
Error for wireless request "Set Tx Power" (8B26) :
    SET failed on device wlan0 ; Operation not supported.

and get no other explainations.. what's the trick?

thanks,
Paolo