wireless - Ubuntu 12.04 Dell 6400 no network

I have just installed Ubuntu 12.04. My network is not working: no wireless, no cable network. There are some posts on forums about it, however I was not able to fix it. It is possible to turn off wireless on my laptop by using the keyboard combination Fn+F2, but how do I check if it is running?

I have found a post with commands to give some info about this problem. Please help, I'm not able to fix it.

marta@martaPC:~$ lspci
00:00.0 Host bridge: Intel Corporation Mobile 945GM/PM/GMS, 943/940GML and 945GT Express Memory Controller Hub (rev 03)
00:02.0 VGA compatible controller: Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller (rev 03)
00:02.1 Display controller: Intel Corporation Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller (rev 03)
00:1b.0 Audio device: Intel Corporation N10/ICH 7 Family High Definition Audio Controller (rev 01)
00:1c.0 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 1 (rev 01)
00:1c.3 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 4 (rev 01)
00:1d.0 USB controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #1 (rev 01)
00:1d.1 USB controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #2 (rev 01)
00:1d.2 USB controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #3 (rev 01)
00:1d.3 USB controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #4 (rev 01)
00:1d.7 USB controller: Intel Corporation N10/ICH 7 Family USB2 EHCI Controller (rev 01)
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev e1)
00:1f.0 ISA bridge: Intel Corporation 82801GBM (ICH7-M) LPC Interface Bridge (rev 01)
00:1f.2 IDE interface: Intel Corporation 82801GBM/GHM (ICH7-M Family) SATA Controller [IDE mode] (rev 01)
00:1f.3 SMBus: Intel Corporation N10/ICH 7 Family SMBus Controller (rev 01)
03:00.0 Ethernet controller: Broadcom Corporation BCM4401-B0 100Base-TX (rev 02)
03:01.0 FireWire (IEEE 1394): Ricoh Co Ltd R5C832 IEEE 1394 Controller
03:01.1 SD Host controller: Ricoh Co Ltd R5C822 SD/SDIO/MMC/MS/MSPro Host Adapter (rev 19)
03:01.2 System peripheral: Ricoh Co Ltd R5C592 Memory Stick Bus Host Adapter (rev 0a)
03:01.3 System peripheral: Ricoh Co Ltd xD-Picture Card Controller (rev 05)
0b:00.0 Network controller: Broadcom Corporation BCM4311 802.11b/g WLAN (rev 01)
marta@martaPC:~$ lsusb
Bus 003 Device 002: ID 1bcf:053a Sunplus Innovation Technology Inc. Targa Silvercrest OMC807-C optische Funkmaus
Bus 005 Device 002: ID 0a5c:4500 Broadcom Corp. BCM2046B1 USB 2.0 Hub (part of BCM2046 Bluetooth)
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 003: ID 413c:8126 Dell Computer Corp. Wireless 355 Bluetooth
Bus 005 Device 004: ID 0a5c:4502 Broadcom Corp. Keyboard (Boot Interface Subclass)
Bus 005 Device 005: ID 0a5c:4503 Broadcom Corp. Mouse (Boot Interface Subclass)
marta@martaPC:~$ ifconfig
lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:912 errors:0 dropped:0 overruns:0 frame:0
          TX packets:912 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:75104 (75.1 KB)  TX bytes:75104 (75.1 KB)
marta@martaPC:~$ iwconfig
lo        no wireless extensions.
marta@martaPC:~$ sudo lshw -C network
[sudo] password for marta:
  *-network
       description: Network controller
       product: BCM4311 802.11b/g WLAN
       vendor: Broadcom Corporation
       physical id: 0
       bus info: pci@0000:0b:00.0
       version: 01
       width: 32 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list
       configuration: driver=wl latency=0
       resources: irq:16 memory:efdfc000-efdfffff
  *-network UNCLAIMED
       description: Ethernet controller
       product: BCM4401-B0 100Base-TX
       vendor: Broadcom Corporation
       physical id: 0
       bus info: pci@0000:03:00.0
       version: 02
       width: 32 bits
       clock: 33MHz
       capabilities: pm bus_master cap_list
       configuration: latency=64
       resources: memory:ef9fe000-ef9fffff
marta@martaPC:~$ lsb_release -d
Description:    Ubuntu 12.04.2 LTS
marta@martaPC:~$ uname -mr
3.5.0-23-generic i686

Please remove the incorrect driver:

sudo apt-get remove --purge bcmwl-kernel-source

Now load your ethernet driver which was blacklisted by the bcmwl driver:

sudo modprobe b44

Now your ethernet should be working. Get a temporary ethernet connection and do:

sudo apt-get install linux-firmware-nonfree

Reboot and everything should be working as expected.