I have a Lenovo Z750 laptop and I had recurring wireless problems in ubuntu and windows, notably the wireless would hang and then appear to be disabled by hardware switch. My method to fix the problem was restart the laptop and set the wireless settings back to factory settings, this was a pain and made using the internet impracticable.
I tried many different drivers, you must make sure that you only have one driver installed. Sometimes there are a number of drivers which would work for your wireless card. Type:
02:00.0 Network controller: Broadcom Corporation BCM4313 802.11b/g/n Wireless LAN Controller (rev 01)
Subsystem: Broadcom Corporation Device 051b
Kernel driver in use: wl
Kernel modules: wl, bcma, brcmsmac
Find the network controller, perhaps purge drivers you don't want!
This didn't work for me, so I tried a friends wireless usb stick because I was getting mad.
At the same time I swapped wireless cards with another laptop Dell mini 10v, my wireless card worked fine in the other laptop so I was happy that it worked. When I put the wireless card back into the original laptop Z570, I have never had a problem since.
Check the warranty though should be fine, was for me.