Thanks, I will check the Console.
I have been talking a lot with NTT support (NTT is the biggest telecommunications compary in Japan) about this, and we found some potential problems with my settings. I had set up my AirPort Express to connect to the ISP over PPP, but the modem was also set up for that, meaning that the provider's server would see me as two userst trying to log in. Now I have switched over the AirPort Express to bridge mode and DHCP, so that the modem/router will assign machines connected to the AirPort an IP address. I also have an Ethernet hub connected to the AirPort, so I can connect my printers and other devices to the Network as well.
This setup has been working for two days now, but the hickup I mentioned ("no cable") actually happened before that, when I had simplified everything and connected two machines directely to the modem. That was a bit of a shocker.
Anyway, for the time being everything seems to be working. I will try the Console if the connection drops again (when it did, the other machine did not drop its connection, so that is suspicious).
Thanks again. Unfortunately, the problems are back again. Had a stable connection and connected the AirPort again. Everything was working fine. Then all of a sudden the connection dropped again today.h
Connected a LAN cable directly to my MacBook Air and got the connection to work immediately.
Took that cable and connected to my MacMini, again, connection came back immediately.
The AirPort (in Brigde Mode) is also connected, but gives me a blinking orange light, and the same "no cable or (modem) is not responding" message again.
I guess this must rule out hardware problems in the computers.
Ligth for the LAN cable port on the modem connected to AirPort is dead. Moved the cable to another port, light still dead.
Shut down AirPort Express, still same orange blinking light when I switched it on.
I now suspect there is something going on with the AirPort Express. Just bought it, and I had the same problem with it's predecessor, but...
Is there any way to trouble shoot the AirPort Express?
I can connect to it Wirelessly, But AirPort Utility says it has been removed from the Network. In the Network Preferences it says it has a self-assigned IP. For Network Settings I get green lights for everything except Network Settings, which gives me a yellow light. It also says the Internet connetcion is working correctly.
Indeed, when I made the direct Ethernet connection inactive I still get a working connection over WiFi, in spite of the blinking orange light on the AirPort and a yellow light for Network settings in Prefereces....
In the console things look normal:
8/7/12 10:04:27.269 PM Apple80211 framework: