2.8 GHz i7, 10.8.4 iMac. In the past few weeks, this iMac's WiFi performance has become very irregular and unreliable. While it shows a strong WiFi signal, it will often not connect, report "connection timeout" errors, start loading pages then stop uncompleted, etc. Occasionally it will have 'bursts' of normal performance for a few minutes, though mostly now it leans toward connection timeout behavior. I'm pretty certain it's not a hardware problem because if I boot to an external drive (10.6) the WiFi connection performs brilliantly. We also have a Macbook Pro and iPad that both connect to the same WiFi in the same house and also connect without any problem. So it's pretty safe to say the 10.8.4 system has some sort of software issue causing this. I've tried repairing permissions, repairing via Disk Utility (reports the disk ok), updated Airport Utility, and running Disk Warrior -- nothing has worked. Has anyone else experienced this, or has any suggestions for troubleshooting this problem?