I installed ubuntu 12.04 on my acer a0722 netbook last week. And since then, it always freezes when I'm offline. Windows 7 is also installed on the netbook, but it works perfectly. I've chosen the network boot as my first option on the boot menu and I've also upgraded my kernel from 3.2 to 3.4. But the problem of freezing still continues immediatiately I log in (this happens when I'm offline). I have an already installed Broadcom wireless driver, this driver works well for windows 7, but after logging into ubuntu, the computer tries to connect to a wireless connection and then it freezes. Please help me with your suggestions, I really want to work with ubuntu.