[xubuntu] Unable to to switch off wireless hotspot to coect to a wireless network

Hello

I have been using Xubuntu 14.04LTS
My computer is a Lenovo Z570
It is configured for dual-boot Windows 7 which I hardly ever use.
I have been using a wireless coection to a SilverCrest repeater.
Normally this usually works fine, but sometimes it discoects, even though the signal strength is excellent.
While trying to resolve this problem I have somehow inadvertently ruined my network coection.

All Settings > Network now shows Wireless Hotspot ON & Aeroplane Mode OFF
Whenever I try to switch Wireless Hotspot from ON to OFF the Network window closes.
Consequently I am unable to get online wirelessly via Xubuntu.

I can get online via Windows 7 when it is coected to the main modem router.

I have updated the BIOS to version 45CN38WW

I am using another computer ruing Windows to get online, so I can type this.

On my Lenovo I have tried following : Wireless coection troubleshooter

Terminal > nm-tool
wlan0
Type: 802.11 WiFi
Driver: brcmsmac
State: discoected
Default: no

sudo lshw -C network
descritption: Network controller
product: BCM4313 802.11bgn Wireles Network Adaprer
vendor: Broadcom Corp

sudo apt-get install lshw
lshw is already newest version

System Settings > System > Software & Updates > Additional Drivers
Broadcom Corportation: BCM4313 802.11b/g/n Wirless LAN Controller
This device is not working
Clicking on radio button Using Broadcom 802.11 Linux STS wireless driver source from bcmwl-keel-source(propietary) > Apply Changes
jumps back to > Do not use the device

Could someone please tell me what I need to do to resolve this problem?