I was recently having an issue with my Airport Express. I was trying to set it up so that I could play music through it. I got it to join my network, but I couldn’t connect to it in iTunes. When I went to go reconfigure it, I found that I also couldn’t connect to it…even though I could see it. I kept getting an error message:
An error occured while trying to access the Apple wireless device. Make sure your network connection is valid and try again. Error 10057
The problem turned out to be a subtle configuration setting with my WiFi. My network is set for WPA with TKIP encryption. However, it appears that Airport Express doesn’t really like to play well with TKIP. Switching the encryption to WPA with TKIP and AES (also called TKIP+AES) fixed the issues. Presumably, setting the network encryption to WPA with AES would also work.
I tried confirming my findings, however I wasn’t able to find anything in the manual or tech specs.
Hopefully, this post helps someone else with a similar problem.