Wireless ZyAir G-220 w/ Linux (zd1211rw)

Hi,

I try to use the Wifi USB adapter ZyAir G-220 (ZyXEL) with Fedora 9
(Kernel 2.6.25.14). However, I don't get any IP from the Router (unknown
type/brand), dmesg shows:
wlan0: privacy configuration mismatch and mixed-cell disabled - disassociate

Here is how I proceeded:

lsusb shows:
Bus 001 Device 002: ID 0586:3401 ZyXEL Communications Corp. ZyAIR G-220

According to lsmod the driver zd1211rw is loaded. The network is
"secured" with WEP. Key and ESSID are set using iwconfig. (I tried using
system-config-network as well.)

If I try to bring the interface up ("ifup wlan0") I get a "failed" after
some time.

dmesg shows:

wlan0: Initial auth_alg=0
wlan0: authenticate with AP 00:13:49:08:5d:8c
wlan0: RX authentication from 00:13:49:08:5d:8c (alg=0 transaction=2
status=0)
wlan0: authenticated
wlan0: associate with AP 00:13:49:08:5d:8c
wlan0: RX AssocResp from 00:13:49:08:5d:8c (capab=0x471 status=0 aid=1)
wlan0: associated
wlan0: switched to short barker preamble (BSSID=00:13:49:08:5d:8c)
ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
wlan0: disassociate(reason=3)
wlan0: privacy configuration mismatch and mixed-cell disabled - disassociate
wlan0: privacy configuration mismatch and mixed-cell disabled - disassociate
wlan0: privacy configuration mismatch and mixed-cell disabled - disassociate
[...]

The last message is repeated several times.

I was able to use this adapter with an older version of Fedora some time
ago.

Any hints?

Thanks,

Norbert