Hello!

I've got a problem with the new network manager. Until last week, I was running Fedora 18 KDE with the old network manager, and I could connect to every single wifi connection I could. Then, I installed Arch with KDE, and it came with the new network manager. And then my problems began. At home, with a simple wireless network only for a dozen devices, with a home router, my laptop connects instantaneously to the wifi network, but at my university I can't connect to any wireless connection. But there I can connect normally in Windows.

I was thinking it was a problem with Arch, so I booted up a live Fedora 20 KDE in a flash drive and it couldn't connect either! The only thing in common with the two is the new network manager. When the connection fails in both distros, two KDE notifications pop up:

"Wireless interface wlan0 - The WiFi network could not be found"
"Wireless connection (name) was disconnected"

I typed some commands to gather information about my hardware, which I post below. It may be not the complete information, because I write everything down in a piece of paper, because I need to reboot back and forth from Windows in order to use the internet. My laptop is a Lenovo Thinkpad T420:

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$ uname - r
3.12.7-2-ARCH

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$ lspci -nn
03:00 Network Controller Intel Corporation Centrino Advanced-N 6205 [Taylor Peak] (rev 34)
Subsystem: Intel Corporation Centrino Advanced-N 6205 AGN
Kernel driver in use: iwlwifi
Kernel modules: iwlwifi

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$ ip link
wlan0: <NO-CARRIER, BROADCAST, MULTICAST, UP> mtu 1500 qdisc mq state DOWN mode DORMANT group default qlen 1000
link/ether (local ip) brd ff:ff:ff:ff:ff:ff

dmesg relevant lines are

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$ dmesg
IPv6 ADDRCONF(netdev_up) wlan0 is not ready
wlan0: authenticate with (access point IP)
wlan0: direct probe to (access point IP) (try 1/3)
wlan0: direct probe to (access point IP) (try 2/3)
wlan0: direct probe to (access point IP) (try 3/3)
wlan0: authentication with (access point IP) timed out

I tried to disable IPv6, but with no avail, by creating a file /etc/sysctl.d/40-ipv6.conf

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# Disable IPv6
net.ipv6.conf.all.disable_ipv6=1
net.ipv6.conf.wlan0.disable_ipv6=1

And, finally, I tried connecting manually with wpa_ commands, but my university's network require authentication with username and password. I have access to two main networks, one open, unsecured connection, which needs to be authenticated in browser to use and other with WPA2 and PEAP authentication. I tried the commands below, but I couldn't manage to make it work:

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$ wpa_passphrase (network name) (network key) > my.conf
wpa_supplicant -B -i wlan0 -c my.conf
dhcpcd wlan0

Have you tried wicd? See, if you can repeat this odd behaviour...

Also, please check the NetworkManager log files to see if they indicate any problems - it usually logs into /var/log/NetworkManager.log or similar.
Based on that dmesg output however, I suspect it is the wireless driver which may be at fault. Could you try a different kernel?