I have Skype 4.2 on Ubuntu 13.04. Sometimes, Skype randomly freezes. I have to Force Quit it. I try to re-start Skype, its icon on Unity blinks to indicate it's loading. But nothing happens. The background of the icon turns back to transparent. It can't re-start. I have to shutdown my PC and restart Ubuntu, it's very tedious. Is there a way around this so that I don't have to restart my whole PC just to re-start Skype?