[other] Sudden lock-ups and reboots (kernel NULL)

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http://ubuntuforums.org – Hi all, Since two weeks or so my system sometimes suddenly locks up (ubuntu 12.04). Meaning that I can see my screen, but mouse/keyboard doesn't work and when I press the power button (short) it doesn't suggest to shut down. Other times it will just reboot randomly. Then when it starts up again it will hang on the boot check 9/10 times. So I think it's a hardware issue. I started off by running memtest86 from a livecd. It would also just randomly hang on 7% or so. So I started it again and another hang! But when it fully ran it said it passed all the test. I recently (about a month or so ag (Hardware)