Advice please>>Belkin N600 DB Router and Airport Express
I need some advice trying to connect an Airport Express (N) to a Belkin N600 DB router. It is for my friend. She had an old router to which I previously successfully connected an older Airport Express (b/g) without issue. Unfortunately her router died and she was led to purchase a Belkin N600 DB which is N only. That is up and running without issue. So I know she had to upgrade to the new Airport Express to be N compatible to continue to get her beloved Airtunes. However, I have not been able to get it installed. I see the AE network from Airport Utility. Can access it and it appears to go through the steps of configuration. But then it seems to time out in the updating step and I get "An Unexpected Error has occurred". At that point the AE cannot be seen until I do a factory reset on it. So it seems to get partially configured but then not able to access the network.
I have tried to troubleshoot best I can:
1. Her wireless network has a good signal and I can easily get on the internet from any number of devices.
2. I took the AE to my house (where I have a Time Capsule and AE) and had it running on my network in about 5 minutes so I am sure the device is good.
3. I hardwired the AE to her router and was able to configure it successfully (green light) I then changed the settings to extend wireless network and again an amber flashing light.
A web search left me confused as folks talk about vendors other that Apple not being compatible with Apple's WDS but all of those posts are several years old and I know I had her old AE working with her old router.
Is there some security setting on Belkin routers that I need to change or make them otherwise incompatible with AE? Does Belkin somehow block other wireless devices on its network? Somewhat frustrated so any ideas or advice would be helpful. Thanks in advance.
Mac OS X (10.7.4)