I have never used wubi, nor do I know how it works or how it may affect drivers and networking. But still...
For a very brief overview how to get wireless networking going in Ubuntu: From the System menu, select Administration, Hardware Drivers. There you should be able to install the drivers for your BCM4311 card. When that is done, restart your computer. After having logged in again you should be able to find your network in the Network Manager icon in the top right of your screen.