I have a lenovo Y400 laptop. And I have installed ubuntu 12.04 on this laptop. When I began to install, I can connect to my wifi router in the Graphical installation mode, and the firefox was useful to surf the internet. But, when finished the installation, I cannot connect to WIFI stably. And, if someone need to connect to my wifi router,only he just need is the password.I can confirm my wifi router works very well , because I can use my mobilephone to connect to it. Why I said "stably"? When I start the Ubuntu, Wifi signals can be found, and I input the password, at this time, I can connect to my wifi router.Then, about 30s to 1min, the wifi module disconnect to the router automatically.Every time, I start the ubuntu, the fuction is normal, after 1min, this problem occurs. I am very confused that why I can connect to my wifi router in the Graphical installation mode, but can't after finishing the installation. Help me please, thanks!