working wireless card stopped working on previously working wireless Ubuntu 11.04

[Abhishek Dixit]

I have a Dell Laptop on which wireless and every thing used to work
perfectly.Today morning I noticed the suddenly there is no wireless at
all. On a working condition I used to have folllowing

lspci -vnn

0c:00.0 Network controller [0280]: Broadcom Corporation BCM4312
802.11b/g LP-PHY [14e4:4315] (rev 01)
    Subsystem: Dell Wireless 1397 WLAN Mini-Card [1028:000c]
    Flags: bus master, fast devsel, latency 0, IRQ 17
    Memory at f69fc000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel driver in use: wl
    Kernel modules: wl, ssb
and

/etc/lsb-release
Ubuntu 11.04 64 bit
Module in use was wl.ko But now all of a sudden it fails to load any
module for wireless.I have no idea why this happened.I am a SOHO user
who does not have any thing other than web surfing and multimedia to
do on this machine.I even booted from a Live USB but still wireless
here failed to work (prior to installation same Live USB was able to
detect the wifi card and wireless worked with this live USB). The
driver in use was found on the LIVE cd at following location

pool/restricted/b/bcmwl/bcmwl-kernel-source_5.100.82.38+bdcom-0ubuntu3_amd64.deb
which used to show as additional drivers available for
installation.Now this option even does not come when I boot with this
Live USB.Since the installation of Ubuntu I have kept this Live USB as
a backup. Can some one help here?