Wi-Fi has stopped working around the time 10.7.3 update. Might they be related?
From what I've seen - this seems to be more a network routing issue than a hardware / link level problem. The first step is to narrow down if it's a network issue or a hardware issue.

In Finder, Shift+Command+G Go to the folder /System/Library/CoreServices and run the two Lion diagnostic tools to assist in narrowing down your problems.


Wi-Fi Diagnostics
Network Diagnostics


Once you have narrowed down the issue, you can ask a second, more detailed question on how to solve a failing step X in diagnostic Y if you still need help in getting this sorted.



This process was used (as described in the comments) to determine that Little Snitch and the existing firewall were causing the network issues.