False firmware for Prism54 wifi usb adapter (p54 driver)

From the LiveCD of Intrepid (or after a fresh installation) the following wifi usb adaptor:
Bus 005 Device 004: ID 0846:4210 NetGear, Inc. WG121 WiFi (v2)
results to the following error in dmesg:
[ 22.528195] prism54usb: eeprom read failed!
[ 22.528219] prism54usb: probe of 5-7:1.0 failed with error -22

Regarding the information I have found here:
http://wireless.kernel.org/en/users/Drivers/p54
I just executed:
sudo wget -O /lib/firmware/isl3890usb "http://jbnote.free.fr/prism54usb/data/firmwares/p54u_2.5.6.0.arm"
which fixed the problem.

Comparing the firmware recommended for pre 2.6.28 in the link given above with firmware found in intrepid shows that only the isl3890usb file doesn't match:

$ ls -Gl intrepid_linux-firmware_1.2/
-rw-r--r-- 1 kostas 29024 2008-10-27 06:33 isl3886
-rw-r--r-- 1 kostas 30060 2008-10-27 06:33 isl3887usb_bare
-rw-r--r-- 1 kostas 93996 2008-10-27 06:33 isl3890 <--- file size doesn't match

$ ls -Gl recommended_pre_2.6.28/
-rw-r--r-- 1 kostas 29024 2009-03-08 15:15 isl3886
-rw-r--r-- 1 kostas 30060 2009-03-08 15:15 isl3887usb_bare
-rw-r--r-- 1 kostas 30176 2009-03-08 15:15 isl3890usb <--- reference

In a following step I tried jaunty alpha5 from a LiveUSB and the wifi adapter didn't work either. Then I compared the firmware files included in jaunty with them recommended at wireless.kernel.org for kernel 2.6.28. None matches, jaunty just includes the same files as intrepid.

$ ls -Gl jaunty_linux-firmware_1.9/
-rw-r--r-- 1 kostas 29024 2009-02-20 19:51 isl3886
-rw-r--r-- 1 kostas 30060 2009-02-20 19:51 isl3887usb_bare
-rw-r--r-- 1 kostas 93996 2009-02-20 19:51 isl3890

$ ls -Gl recommended_2.6.28/
-rw-r--r-- 1 kostas 29160 2009-03-08 15:14 isl3886
-rw-r--r-- 1 kostas 28980 2009-03-07 20:27 isl3887usb_bare
-rw-r--r-- 1 kostas 29500 2009-03-07 20:27 isl3890usb

I also tried to replace the firmware files with (the ones recommended for 2.6.28):
sudo wget -O /lib/firmware/isl3890usb "http://daemonizer.de/prism54/prism54-fw/fw-usb/2.13.1.0.arm.0"
and
sudo wget -O /lib/firmware/isl3887usb_bare "http://daemonizer.de/prism54/prism54-fw/fw-usb/2.13.1.0.arm.1"
but it didn't worked.

I also tried the variant of the firmware which had worked in intrepid (recommended for pre-2.6.28):
sudo wget -O /lib/firmware/isl3890usb "http://jbnote.free.fr/prism54usb/data/firmwares/p54u_2.5.6.0.arm"
but with no luck.

In jaunty I couldnt get the wifi adapter to work at all.