I (linux newbie) have a Dell XPS 17 and tried to install Ubuntu 12.04. After installation all WLAN accesspoints near are detected. But I can not connect (but I am able to connect with other computers as well as with Dell XPS 17 under windows). Outputs:

iwconfig

  lo        no wireless extensions.

  wlan0     IEEE 802.11bg  ESSID:"LerchenPoint"  
      Mode:Managed  Frequency:2.412 GHz  Access Point: 58:6D:8F:A0:2D:58   
      Bit Rate=1 Mb/s   Tx-Power=14 dBm   
      Retry  long limit:7   RTS thr:off   Fragment thr:off
      Power Management:off
      Link Quality=70/70  Signal level=-37 dBm  
      Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
      Tx excessive retries:0  Invalid misc:19   Missed beacon:0

  eth0      no wireless extensions.

sudo lshw -class network

*-network               
   description: Wireless interface
   product: Centrino Wireless-N 1000
   vendor: Intel Corporation
   physical id: 0
   bus info: pci@0000:04:00.0
   logical name: wlan0
   version: 00
   serial: 00:26:c7:99:98:28
   width: 64 bits
   clock: 33MHz
   capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
   configuration: broadcast=yes driver=iwlwifi driverversion=3.2.0-24-generic firmware=39.31.5.1 build 35138 latency=0 link=no multicast=yes wireless=IEEE 802.11bg
   resources: irq:50 memory:f0400000-f0401fff
*-network
   description: Ethernet interface
   product: RTL8111/8168B PCI Express Gigabit Ethernet controller
   vendor: Realtek Semiconductor Co., Ltd.
   physical id: 0
   bus info: pci@0000:0a:00.0
   logical name: eth0
   version: 06
   serial: f0:4d:a2:56:e3:94
   size: 1Gbit/s
   capacity: 1Gbit/s
   width: 64 bits
   clock: 33MHz
   capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp
   mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
   configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl_nic/rtl8168e-2.fw ip=192.168.0.123 latency=0 link=yes multicast=yes port=MII speed=1Gbit/s
   resources: irq:47 ioport:6000(size=256) memory:f0a04000-f0a04fff memory:f0a00000-f0a03fff

dmesg | grep iwl

[   10.157531] iwlwifi 0000:04:00.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17
[   10.157561] iwlwifi 0000:04:00.0: setting latency timer to 64
[   10.157598] iwlwifi 0000:04:00.0: pci_resource_len = 0x00002000
[   10.157599] iwlwifi 0000:04:00.0: pci_resource_base = ffffc90011090000
[   10.157601] iwlwifi 0000:04:00.0: HW Revision ID = 0x0
[   10.157731] iwlwifi 0000:04:00.0: irq 50 for MSI/MSI-X
[   10.157834] iwlwifi 0000:04:00.0: Detected Intel(R) Centrino(R) Wireless-N 1000 BGN, REV=0x6C
[   10.157976] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S
[   10.179772] iwlwifi 0000:04:00.0: device EEPROM VER=0x15d, CALIB=0x6
[   10.179775] iwlwifi 0000:04:00.0: Device SKU: 0X50
[   10.179777] iwlwifi 0000:04:00.0: Valid Tx ant: 0X1, Valid Rx ant: 0X3
[   10.179796] iwlwifi 0000:04:00.0: Tunable channels: 13 802.11bg, 0 802.11a channels
[   10.574728] iwlwifi 0000:04:00.0: loaded firmware version 39.31.5.1 build 35138
[   10.726409] ieee80211 phy0: Selected rate control algorithm 'iwl-agn-rs'
[   19.714132] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S
[   19.777862] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S
[ 2251.603089] iwlwifi 0000:04:00.0: PCI INT A disabled
[ 2266.578350] iwlwifi 0000:04:00.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17
[ 2266.578399] iwlwifi 0000:04:00.0: setting latency timer to 64
[ 2266.578435] iwlwifi 0000:04:00.0: pci_resource_len = 0x00002000
[ 2266.578437] iwlwifi 0000:04:00.0: pci_resource_base = ffffc90011090000
[ 2266.578439] iwlwifi 0000:04:00.0: HW Revision ID = 0x0
[ 2266.578704] iwlwifi 0000:04:00.0: irq 50 for MSI/MSI-X
[ 2266.578808] iwlwifi 0000:04:00.0: Detected Intel(R) Centrino(R) Wireless-N 1000 BGN, REV=0x6C
[ 2266.578916] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S
[ 2266.600709] iwlwifi 0000:04:00.0: device EEPROM VER=0x15d, CALIB=0x6
[ 2266.600712] iwlwifi 0000:04:00.0: Device SKU: 0X50
[ 2266.600713] iwlwifi 0000:04:00.0: Valid Tx ant: 0X1, Valid Rx ant: 0X3
[ 2266.600727] iwlwifi 0000:04:00.0: Tunable channels: 13 802.11bg, 0 802.11a channels
[ 2266.605978] iwlwifi 0000:04:00.0: loaded firmware version 39.31.5.1 build 35138
[ 2266.606331] ieee80211 phy0: Selected rate control algorithm 'iwl-agn-rs'
[ 2266.614179] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S
[ 2266.681541] iwlwifi 0000:04:00.0: L1 Enabled; Disabling L0S

Solutions I tried:

rfkill list all

0: dell-wifi: Wireless LAN
Soft blocked: no
Hard blocked: no
2: phy0: Wireless LAN
Soft blocked: no
Hard blocked: no

echo "options iwlwifi 11n_disable=1" | sudo tee /etc/modprobe.d/iwlwifi.conf

options iwlwifi 11n_disable=1
sudo modprobe -rfv iwlwifi
  WARNING: All config files need .conf: /etc/modprobe.d/blacklist, it will be 
  ignored in a future release.
  rmmod /lib/modules/3.2.0-24-generic/kernel/drivers/net/wireless/iwlwifi/iwlwifi.ko
  rmmod /lib/modules/3.2.0-24-generic/kernel/net/mac80211/mac80211.ko
  rmmod /lib/modules/3.2.0-24-generic/kernel/net/wireless/cfg80211.ko
sudo modprobe iwlwifi
  WARNING: All config files need .conf: /etc/modprobe.d/blacklist, it will be 
  ignored in a future release.

replacing iwlwifi-1000-5.ucode (current driver) against iwlwifi-1000-3.ucode

sudo jockey-gtk:

(jockey-gtk:2493): Gtk-CRITICAL **: gtk_icon_set_render_icon_pixbuf: assertion icon_set != NULL' failed (jockey-gtk:2493): Gtk-CRITICAL **:   gtk_icon_set_render_icon_pixbuf: assertion icon_set != NULL' failed 

nothing is listet in "Additional drivers" (german: "Zusätzliche Treiber").

gksudo gedit /etc/modprobe.d/blacklist.conf

add "blacklist acer_wmi"

Any help would be appreciated very much.

Thanks!!