Ever since the upgrade to Apple OS X Mountain Lion (10.8) on my MacBook (v5.1) I encountered wireless problems every now and then. These 'experiences' are documented in two different blog posts here and here.
At the time I was also running an 'old' version of Little Snitch (v2.x). After installing v3.0.1 my problems seemed to have solved... Seemed, until I upgraded Little Snitch to v3.0.2.

After the (mandatory) reboot my wireless connections were gone. The adapter wouldn't go active. The symptoms being the exactly the same as before. So I have no doubt, that Little Snitch had something to do with it.