[System] Kubuntu stops loading after login screen

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http://www.kubuntuforums.net – Hi, Looking for some help! I've been running Kubuntu happily for 6 months, yet I have tried to log in today and have some problems... Basically, I load Kubuntu as normal, the PC loads up the logon screen, I enter my password and nothing happens. The mouse pointer still works but KDE doesn't load. I've tried CTRL + ALT + F6 to get to a console, but I just get a flashing - . PC is a desktop, Dell, 64 bit, nvidia graphics, core i5 CPU, 8gb ram. Kubuntu 13.04. Thanks (HowTos)