Wifi Won't Connect; Connection Timeout (Mac) I'm having issues with my macbook pro OS X 10.7.5.  It used to connect to the wifi router (D-Link N300, DIR=615) no problems.  But for the past several weeks, I haven't been able to at all.

What pops up when I select my wifi network from the list:


"Failed to join "network"
A connection timeout occured".


What happens when I try to enter my password manually:


"Connection timeout"


What I've tried to do as solutions:


Google
Restart router by pressing reset &amp; refresh button
Delete System &amp; User (Login) Keychain access
Network > Gear symbol by the + and - bottom left of the screen > Set Service Order > Drag Wifi to the top
Been there, done that. I found the source to my problem, but not something that might be a general answer for all with this problem. 

After exhausting the other answers here, I just started trying anything. What I discovered was that I have an external HD connected by firewire, and had it running when I rebooted after installing software. With the drive running, no connection. I shut off the drive and it immediately connected. Go figure! It runs fine of I start the drive after startup, but not during. (Mac Mini C2D 2.54, OS X 10.8.3)

Perhaps the wires acted as antenna or otherwise changed the power available to the Wi-Fi chipset, but I'm not seeing these timeouts after changing my connected devices and cables.