I had a problem with skype ( http://www.linuxquestions.org/questi...d.php?t=523334 ),
enigmaticly solved, that now appeared again...when i open the application my computer freezes and i cannot do anything apart from turning it off from the power button and restart...the same happens when i use qbittorrent and some other times randomly...can anybody advice anything?in this conditions the system is really too unstable..i'm new to linux and i don't know where to start...thank in advance...

Could be a hardware problem... First, check if your system hangs totally or if it's only the X server: when it hangs again, try going to a console by pressing Ctrl + Alt + F1. If a text login screen shows up, it's only the X server that crashed. If this doesn't work, try pressing Num Lock. Does the keyboard LED switch on and off? If not, your kernel probably panicked. This is likely to be caused by either a bug or a hardware problem. Does it only happen when using programs that connect to the internet? In that case, it might be caused by bad support for your network card.