Need help with Apple Airport Express


I bought an Apple Airport Express so I can connect my Marantz SR-7007 to my wireless network. I want to use it as a wireless client. I have an iMac and AT&T uverse is my Internet provider. The Airport Express configures properly ONLY IF it is connected to the router with an Ethernet cable. I can not get it to work with the Wireless network. I've googled directions and tried everything. Can anyone help, or do I have to have an Apple tech come to the house ? Thanks
mabonn
"Dropouts again! Went almost a week with no dropouts. Then today I downloaded a Dave Brubeck album from HD Tracks. It's FLAC 24 bit 88.2 kHz. It drops out every minute or two. Internet radio and my CDs (FLAC 16 bit 44.1 kHz) are still ok. Any suggestions ?"

Is it possible that there could be a problem with the files themselves? It might be worth it to burn the files to a CD. If the drop outs are on the CD then you may have some damaged downloads.
ZD542, I don't think it's the file, because it streams with no dropouts to my Logitech Squeezebox Touch. So far, I have downloaded 2 albums from HD Tracks, one is 96khz, and the other is 88.2 kHz. Dropouts occur only on the AE, no dropouts on the SBT.
Almarg, The software serving the music is the Logitech Media Server running on an iMac. So far, I have not been able to increase the buffer size on the server software, the AE, or the receiver. I'll try consulting with dealer I purchased the receiver from, and Apple tech support. I may just go for a dual band router. I have browsed lots of forums, and it turns out there is lots written on this problem, but no one definitive solution. The only bullet proof solution is to hard wire the AE to the router. I really want to go wireless.
Again, thanks for all your help and suggestions. ....Matt
Mabonn, I had impression that AE is limited to 16 bit, but if it is the case you should have no sound at all.
Kijanki, I had more dropouts after I thought I had eliminated them. So, I went to Best Buy and bought a Linksys 2500 dual band router. Got it set up today, and it seems to be working. If it goes an entire week with no dropouts, I'll declare victory. The one question I have (for now) is this: Wireless devices are given the option of joining the secured network with password or as a guest (unsecured with no password). How do I disable the "guest" option? Thanks, Matt
You will find in System-Router menu: Setup, Wireless, Security etc..

Select Wireless. It will open Basic Wireless Settings, Wireless Security, Guest Access etc. Select Guest Access. It will show option "Allow Guest Access" Yes/No - select "No".

Guest possibly cannot change settings but I have no use for this option and disabled it.