I have installed Ubuntu 12.04 on Dell Inspiron 1525. After the installation I found out that wireless connection does not work. I was able to connect to the internet via cable. Then I found out that many people have similar problems and read through many posts yet I wasn't able to solve it so here is what I tried.
System->AdditionalDrivers->Broadcom STA wireless driver produced message "Sorry, installation of this driver failed."
Then I installed Synaptic package manager and tried to reinstall and also remove and install bcmwl-kernel-source it always said something like that installation failed (yet synaptic was showing green light next to it)
I regularly rebooted to see if there is any change but haven't seen one.
Then I tried removing bcmwl-kernel-source and adding b43-fwcutter and firmware-b43-lpphy-installer after reboot there was a change. I was able to see options in the menu for connection (up right) like "Enable Wireless" but at the place where I'd expect the list of networks is only (grayed) "Wireless Networks Disconnected" - And they should be there since I was able to connect with other computers, even with Live Ubuntu.
some other info from terminal (in the last state of system described)
katka@katka-Inspiron-1525:~$ lspci | grep 'Network'
0b:00.0 Network controller: Broadcom Corporation BCM4312 802.11b/g LP-PHY (rev 01)
katka@katka-Inspiron-1525:~$ sudo iwconfig
wlan2 IEEE 802.11bg ESSID:off/any
Mode:Managed Access Point: Not-Associated Tx-Power=20 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
lo no wireless extensions.
eth2 no wireless extensions.
katka@katka-Inspiron-1525:~$ rfkill list
0: hci0: Bluetooth
Soft blocked: no
Hard blocked: no
1: phy0: Wireless LAN
Soft blocked: no
Hard blocked: no
This is as much as I was able to get from other posts and now I don't now what to do next.