existing devices would connect flawlessly to my wireless network but new devices would not.
Didn't matter whether it was a PC or a Mac, iPod or iPad, if it was new, then it would not connect.
The fix was to power off the Wireless Router, physically remove the power supply, and then plug it back in again.
Once rebooted, everything joined the wireless network without a problem
P
Help! I have tried helping a friend who has just bought 2 iPads, a 2 and a 3, both wifi only. I took my iPad 3 along and got an immediate connection on his Orange wifi network and also on my iPhone 4. We took the new iPads out of the box and although the wifi is picked up both iPads refused to make a connection. I have to say the wifi signal is picked up by his Kindle and HP ePrinter. I have tried everything, even bringing them home and connecting them to my cable wifi network, which they do seamlessly, but when I took them back - no connection. I have tried several fixes suggested on web sites, including resetting the Network but to no avail.
In summary then. the Orange wifi connects to my iPad 3, iPhone 4, Kindle and HP ePrinter. Both iPads connect to my wifi but not to his Orange wifi. I am getting desperate now.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic