What Wi-Fi router, port, switch or WAP do you use?
It could be that the device is no supported with OS X Lion, but it should be as the Utilities are the same in Lion as they are in Snow Leopard.
Check the settings on your MBP and router as some of them could be blocking each other.
Is your MBP searching/registering that there is a Wi-Fi signal or just not working at all?
Finally, if none of that works...
You should have a copy of OS X 10.6 on a disk when you bought our MBP.
Called Apple they were amazing 1st I had to call in 2yrs. Deleted all networks, something in keychain, system library folder restarted and it worked. Then the Comcast guy came gave me a new gateway (took old router and modem away), then I had the same problem all over. Called Apple back they walked me through the steps again.
Life is good.