A persistent, flashing amber light indicates that any of the several potential conditions may require your attention:
o The base station has not yet been configured because it is new, or the reset switch has been set.
o You have selected a security configuration that is not recommended.
o One of several other conditions, such as a disconnected Ethernet cable or invalid IP address has been detected.
If you run the AirPort Utility, it will show an amber circle on the summary page next to the area(s) causing the problem. Click on this amber circle and it should provide an explanation.
Thanks for the tip Tesserax! I have been experiencing the blinking yellow light issue for some months, but never did anything because my DSL connection continued to work. I would reboot my airport extreme and the light went green for about two weeks, then it would start to blink yellow again. So on a whim I checked the Apple Support Community and did a search under "Airport Extreme Yellow Blinking Light", and found this discussion. I read about the airport utility and checked it out. At which point I found that I had airport extreme firmware version 7.4.2. A newer version 7.5.2 was available. The utility prompted me to download the firmware update which I did. Within a few minutes the download was complete and my airport extreme rebooted itself. The utility verified that all was in working order; and I now have a green light! This is what I love about Apple and the Apple community. I can find information similar to an issue I am having. Get pointed in the right direction. Then do a couple of simple things and all is fixed. No screwing around with stuff. Things just WORK! I am so glad I have Apple computers and software. Nothing beats them. Nothing. Thanks Apple!