[kubuntu] Kubuntu becoming unresponsive

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http://ubuntuforums.org – My Kubuntu pc boots up and runs fine for a short while (10 minutes or so) then something starts blinking in the lower right (about where the show desktop hotspot is in Windows 7) and the system becomes unresponsive. The only thing I can do is power it down. Any ideas why it is doing this? (Hardware)