The Mac OS X 10.7.3 update appears to have a bug that disconnects your wireless network when you wake from sleep, requiring that you manually re-select the wireless network. Apple has released an patch for late 2009 and newer iMacs to fix this, however many users are reporting this issue with MacBooks, MacBook Pros, and MacBook Airs. If you have an iMac experiencing this problem, make sure to apply Apple’s iMac Wi-Fi Update v1.0. Hopefully Apple will release a patch for other Mac models soon.