I'm away from home, and my familiar computing setup. I am visiting a friend. I brought both my laptop and desktop computers with me. The laptop is running Ubuntu 11.10, the desktop 12.04.1. I can get the laptop to connect to my friend's wireless modem repeatedly, without problems. My desktop computer, on the other hand, connected for just one session. After I powered the machine down and restarted it, I cannot get it to connect again.
My friend has a Cisco wireless modem. Its internal router is a Linksys EA4500. He uses a WPA2 protocol with a password. Everything is working smoothly with the laptop.
When I started the second session with the desktop machine, what I saw was a long attempt to connect (about 30 seconds). Then the "wireless network authentication required" dialog box appears, as if I didn't have the correct password. I have verified that I do indeed have the right password. I can press "connect" as many times as I like. Thirty seconds later, the dialog box appears again.
I tried connecting to other routers in the neighborhood, just to see if I would get the password dialog box, and I do. I enter a password that I know will not work. The symptoms I see are the same as I see when trying to connect to my friend's router. But in any case, my desktop appears to be establishing an initial connection with any router I might try.
My home router has a setting which can limit the number of wireless devices connected to the network. I shut down the laptop with the idea that I might need to open up a slot for the desktop machine to connect. That didn't change anything. In any case, I asked my friend (a software engineer) whether there was such a setting on his router, and he said no.
At home, my desktop machine is normally connected to our router by wire. I had a hand-me-down wireless-N network card that I had never tried before. It is so generic that the manufacturer's name doesn't even seem to be on it. The model number on the sticker reads "WS-WNP671N", and apparently that card is made by a company called WinStar.
The laptop is old, an IBM ThinkPad Z60m. The LAN hardware is apparently an Intel Wireless Pro card, which comes from the days before the wireless-N protocol. At best, it is connecting to the router using wireless-G.
So I have a few different variables here -- laptop vs. desktop, two different wireless LAN cards, two slightly different operating systems. I'm especially baffled by the fact that the desktop worked once, flawlessly, and now refuses to play an encore.
If any of you have any ideas how to proceed, I would appreciate it. Thanks!