Network manager reports wireless card as "Device Not Managed"

[Rallias Ubernerd]

After upgrading to 11.10, I sometimes get the error in the network manager applet "Device Not Managed" under the wlan0 and wlan1 cards in my laptop. Its always in wlan1 (a USB plug & play linksys 802.11g, don't have it available to me atm), and on occasion the wlan0 card (inbuilt card, no clue what it is). At this point, I go into the terminal and try to set it up with iwconfig, but either I can't figure it out or it doesn't work, because it won't allow me to do anything, even as root.

I run an Asus K50ij laptop, only modification is 4 GB of ram instead of 3.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: network-manager 0.8.9997+git.20110721t045648.36db194-0ubuntu2
ProcVersionSignature: Ubuntu 3.0.0-8.11-generic 3.0.1
Uname: Linux 3.0.0-8-generic x86_64
Architecture: amd64
CRDA: Error: [Errno 2] No such file or directory
Date: Fri Aug 19 10:22:08 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110426)
IpRoute:
 default via 10.0.0.1 dev wlan1 proto static
 10.0.0.0/8 dev wlan1 proto kernel scope link src 10.0.0.148
 169.254.0.0/16 dev wlan1 scope link metric 1000
Keyfiles: Error: [Errno 2] No such file or directory
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
RfKill:
 0: phy0: Wireless LAN
  Soft blocked: no
  Hard blocked: no
SourcePackage: network-manager
UpgradeStatus: No upgrade log present (probably fresh install)

[Mathieu Trudel-Lapierre (cyphermox)]

Please remove or comment out the entries for wlan0 from /etc/network/interfaces:

# The primary network interface
auto wlan0
iface wlan0 inet dhcp
 # wireless-* options are implemented by the wireless-tools package
 wireless-mode managed
 wireless-essid phoenix

With entries for interfaces set up in the /e/n/i file, NetworkManager ignores the interface and considers it not managed.