I kept getting the same error. I could hook fine at my brother's house, but could not access at my own wireless. Drove me nuts! The "expert" at Apple was no help, and he suggested I bring in my Laptop, Router, etc...
Gave it one more try and found a link to Wired Gadgets. I followed their instructions and am now able to access my wi-fi!!!! Woot!!
Here is the link:
http://wiredforgadgets.com/?p=743
And if you're lazy:
You could fix this at your router, but this won’t help on other networks, so you may as well to this your iTouch/iPhone.
Go to Settings.
Select Wi-Fi.
Chose a network.
Select the blue arrow next to the network you are connected to.
Select DNS.
Change the IP Address to 208.67.222.222
The IP address 208.67.222.222 is a service called OpenDNS, which not only is safer, but is guaranteed to work with any network anywhere.
The Catch-22 is that you have to do this with every new Wi-Fi you pick up that doesn’t work. It’ll remember past ones, but it won’t do it to new ones. I recommend writing down the IP Address 208.67.222.222 and keeping it in your wallet for easy access.
Hopefully that solves everyones problems. Be sure to leave a comment if you have any more questions.