Could be a zillion things. The modem. The connection. Ethernet? Wireless? Your ISP. Start by telling us how you are connected to the internet. Cable modem? DSL? Have you tried powering down everything and repowering back up? Are you certain you actually have internet service? Have you tried just conecting to the modem and by passing the router?
So the router and modem work fine with every other device. This seems to be internal with my computer. It is acting the same on both my home and work network. This is over wifi since I don't have an Ethernet port.
Right now my computer sees my work network, it shows a strong signal but when I open a browser it says "server not found". Other times I get the "!" over the wifi bars. Both ways I can't coonect to the server.
Go into System Preferences the Network area highlight the Wi-Fi connection and post the IP address you are getting.
Then open Applications, Utilities, Network Utiltiy and go to the Ping tab and type in Google.com and then hit the enter key or click the Ping button. What do you get in the text window?
It should be "Ping has started"
Ping google.com the an IP and below that do you get any response or does it say timed out.
Do what Shootist007 said first so we can see if even basic connectivity is working and after we see what those results are, you may want to take these steps to see if it fixes the issue.
THIS IS HOW I FIXED IT:
I went to Library->Preferences->SystemConfiguration
I renamed NetworkInterfaces.plist to NetworkInterfaces.plist.bak
I renamed preferences.plist to preferences.plist.bak
Upon re-starting, it worked perfectly. Then, I deleted the bak files. I think this had to do with the two preference files. I knew it had to do with the computer as a whole, but knew it wasn't down to a deep level that would require a re-installation.
I hope this helps out anyone else who is experiencing the same issue.
Go back into Network and the highlight your WiFi and click the Advanced button. Then go to Proxy and see if anything is selected.
What is the IP address your WiFi card is getting. Please post. It is a PRIVATE IP address more then likely starting with 192 or 172 or 10. These are all Private addresses that can not be reach from the internet.
The computer I am on right now has an IP of 192.168.1.100.
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As to your problem.
So you are using an Apple Airport of some type. I say that because Apple routers are the only ones I know of that use the 10.x.x.x IP address as the LAN address by default.
If all other devices you have can connect through your router to the internet then yes it is a problem with the Retina. This is common for the Retina model.
Things you can try.
Delete all WiFi networks and re-enter them.
Create a Test User Account and see if that will connect to INet.
Save your personal files, Wipe the drive and reinstall the OS.
Or since it is still within the standard one year warranty take it to an Apple store Genius Bar and have it fixed.
If you do that don't be surprised if it works fine at the Apple store and they send you on your way. It is my opinion that all Apple stores are directed to use 5Ghz WiFi band that most Mac computer have no problems with but yet those same Mac's can't successfully connect to, and or stay connected to, the 2.4Ghz band WiFi.