Can't configurate my second Airport Express

Hi, I just spent two hours in vain to set up my second Airport Express.

I get Internet from my neighbors via WLAN.

I managed to configurate my first Airport Express (living-room) as a client 'connect with wireless network'. I only use it to stream music to my music center.

I bought a second Airport Express to do the same in the kitchen. The idea is that when I play music with itunes the music will play in the kitchen and in the livingroom. It doesn't work. When I reset and start from the scratch I have four options:

A Create new network

B Join an existing network

C Replace a unit

D Reset old settings

A works but doesn't solve the problem since it won't join the network

B doesn't work, first it is looking good, than there is written 'waiting for the station' for around 4 minutes and than there is an error message ' an unexpected error arrived, try again!'

C is not what I am looking for

D is not what I am looking for

Any ideas what to do? Why can't I join the existing network?

Please help