airport strangeness

[Edward Arrowsmith]

I had no problem connecting to the Internet wirelessly via  
AirportExpress. Recently we moved the Airport base station and added  
an inline ethernet coupler to gain the extension of the ethernet  
cable. Since then we are unable to connect to the web. However,  
network diagnostics shows we have an airport connection, there are  
five bars indicating a strong signal. My iBook thinks it is connected  
by ethernet instead of airport.

Have tried all known (to us) possibilities, any suggestions greatly  
appreciated.

Thanks and best wishes
Janis