I am using Fedora 19 and want to change the date and time in my system. To do so, I clicked on the date and time settings, but the window does not appear. Similarly, I can't change Network Settings because the window does not open. The same is the case for proxy settings in Google Chrome. I have tried this a number of times by restarting the system, but the same problem appears every time. Why is this happening, and how can I fix it?