Airport express connects at first, then blinks amber

Question

i recently moved to a new apartment (new got a new modem from Time Warner) and I cannot figure out how to get the internet working. Each time I perform the reset steps for the Airport Express, the will green light comes on and the internet works, then after a few minutes I get disconnected and the AEx sports a blinking amber light. When I use the Airport Utility tool to troubleshoot, the first error I have is "device does not have a valid IP address".....no clue where to go from there. help!!!!

Answer 1

Download and install Air Radar to get a look at the visible wireless networks around you. Click the Scan button at the lower right of the main window to run a search of wireless networks. The program is free for 15 days.
Let the program run a few minutes and then look for the number of wireless networks that are showing up and more importantly, write down the channels that they are operating on. Run a scan again in 30 minutes or so to see if things have changed.
This won't display all the wireless networks, because most modern routers, Apple included, allow the user to "hide" their network. In other words, it can be operating, but it won't show up on your computer and may not show up on Air Radar. So, it's possible that a network is interfering with your wireless and you won't be able to identify it.
You won't be able to do anything about a neighbor's wireless security system, or a nearby cordless phone (almost all of them operate on the same 2.4 GHz frequency that most wireless networks use, so they cause far more problems than people imagine). When you get ready to test your AX again, if you have a cordless phone, turn it off for an hour or so, just in case. Same for a nearby TV.
When you are ready, you will do a Manual Setup of the AX, but do not do this until you have a survey of other wireless network channels in use around you.
Open AirPort Utility, click Manual Setup
Click the Wireless tab below the row of icons
Wireless Mode is Create a wireless network
Wireless Network Name - Your choice
Radio Mode - 802.11n (802.11b/g compatibel), or if all your computers are "n" capable, you can select an "n" only Radio Mode like 802.11n 2.4 GHz. Hold down the option key when you click on the selection box to see more choices
Channel - Set this to a channel that is as far away as possible from the other channels that Air Radar has picked up. You may need to experiment further with these settings as I suspect there are at least a few "hidden" networks there.
Wireless Security - WPA/WPA2 Personal
Password - Your choice
Click the Music icon to setup AirTunes if you wish
Update to save settings.
If still no luck, go back and change the Radio Mode to 802.11n only 5 GHz. I'm assuming your computer(s) are "n" capable, otherwise they will not be able to pick this up. There are fewer networks on this band, but the signal does not travel through obstructions as well as a 2.4 GHz signal.
You have now done just about everything possible to work through Possibility #3.
If the AX continues to lose it's settings after a short period, you have now moved to Possibility #4.