当我使用 ubuntu 12.04 时，一切都运行正常。我现在使用 Kubuntu 15.04。当我的会话开始时，wifi 连接不到一分钟，之后就断开连接，无法重新连接。
我总是尝试禁用 11n 选项，同时也终止“wpa_supplicant”，但什么也没改变。
这是命令的输出lspci：
03:05.0 Network controller [0280]: Ralink corp. RT2561/RT61 rev B 802.11g [1814:0302]
和iwconfig：
wlan0 IEEE 802.11bg ESSID:off/any
Mode:Managed Access Point: Not-Associated Tx-Power=20 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Power Management:on
尝试重新连接后的一些系统日志：
25/09/2015 20:38:07 chris-System-Product-Name NetworkManager[659] <warn> Activation (wlan0/wireless): association took too long, failing activation.
25/09/2015 20:38:07 chris-System-Product-Name NetworkManager[659] <info> (wlan0): device state change: config -> failed (reason 'ssid-not-found') [50 120 53]
25/09/2015 20:38:07 chris-System-Product-Name NetworkManager[659] <info> NetworkManager state is now DISCONNECTED
25/09/2015 20:38:07 chris-System-Product-Name NetworkManager[659] <warn> Activation (wlan0) failed for connection 'FreeWifi'
25/09/2015 20:38:07 chris-System-Product-Name NetworkManager[659] <info> (wlan0): device state change: failed -> disconnected (reason 'none') [120 30 0]
25/09/2015 20:38:07 chris-System-Product-Name NetworkManager[659] <info> (wlan0): deactivating device (reason 'none') [0]
25/09/2015 20:38:07 chris-System-Product-Name NetworkManager[659] <info> (wlan0): supplicant interface state: scanning -> disconnected
25/09/2015 20:38:07 chris-System-Product-Name NetworkManager[659] <warn> Couldn't disconnect supplicant interface: This interface is not connected.
对此有什么线索吗？