Description:
Cannot switch card into valid monitor mode. Card can connect with access point, but in monitor mode interface always shows PWR=0, no packet injection.

Additional info:
[root@mik-pc mik]# uname -r
2.6.34-ARCH (and 2.6.33)
wireless usb card:
Bus 001 Device 006: ID 0ace:1215 ZyDAS WLA-54L 802.11bg
used module:
zd1211rw

Steps to reproduce:
Insert card into usb port :)
[root@mik-pc mik]# airmon-ng start wlan1


Found 3 processes that could cause trouble.
If airodump-ng, aireplay-ng or airtun-ng stops working after
a short period of time, you may want to kill (some of) them!

PID Name
3373 NetworkManager
3427 wpa_supplicant
4029 dhcpcd
Process with PID 4029 (dhcpcd) is running on interface wlan0


Interface Chipset Driver

wlan0 RTL8187 rtl8187 - [phy1]
wlan1 ZyDAS 1211 zd1211rw - [phy2]
(monitor mode enabled on mon1)
mon0 ZyDAS 1211 zd1211rw - [phy2]

[root@mik-pc mik]# airodump-ng mon0

CH 1 ][ Elapsed: 9 s ][ 2010-08-19 08:41

BSSID PWR Beacons #Data, #/s CH MB ENC CIPHER AUTH ESSID

00:13:46:FA:10:30 0 2 0 0 6 54 WPA TKIP PSK ZEBRA
1C:AF:F7:8A:71:80 0 13 0 0 11 54e. WPA2 CCMP PSK CYPIS
00:22:B0:AC:CC:60 0 4 0 0 3 54 . WPA2 CCMP PSK edyta

When used patching kernel with patch avaiable
wget http://wireless.kernel.org/download/compat-wireless-2.6/compat-wireless-2.6.tar.bz2
tar xfj compat-wireless-2.6.tar.bz2
cd compat-wireless-*
wget http://www.zlaten.biz/tmp/zd1211rw-inject+dbi-fix-2.6.26.patch
wget http://patches.aircrack-ng.org/mac80211.compat08082009.wl_frag+ack_v1.patch
(additional info: http://az.linux.pl/2009/11/zydas-zd1211-aircrack-ng-suite.html)

works fine - injection works, but wireless card cannot connect to any acces point.