Wi-fi sometimes doesn't turn on when netbook wake up after being sent to hibernate state with disabled wi-fi.
The problem with wi-fi was solved by using Broadcom STA driver (bcmwl-kernel-source, broadcom-sta-common, broadcom-sta-source packages were installed)
Update: Power Managenet function in bcmwl-kernel-source driver doesn't work well. WiFi connection degrades once power cord is disconnected. For more info read please: http://uselessuseofcat.com/?p=67
Finally I solved the problem with wi-fi.