I'm kinda new at Ubuntu/Kubuntu, and I had a few issues. For whatever reason, and at random times Kubuntu locks up and I cannot use either mouse nor keyboard. I have tried jumping to terminal mode, but even that doesn't work. Actually, while I was typing this, it crashed and I had to switch to my Eee Pad. I've searched Google, ran diagnostics, and tried to read system logs, with little luck. I think the problem may lie in my graphics, but I'm willing to do anything to fix it.
If it helps at all, when I ran the diagnostics my PC failed the "graphics/display" category.