Ubuntu with a Radon HD6850 crashes with a black screen appearing for seconds

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http://askubuntu.com – A bit of a weird one. Ubuntu regularly freezes and the screen goes black for a few seconds then comes back. After coming back all the applications are frozen yet I have control over the mouse again. After about 5-10 seconds the screen will then go black again for a few seconds and this repeats indefinitely as far as I have tested. The only thing I can do is hard reset. I haven't exactly been stressing it out with any heavy applications and my spec (3.4ghz quad core, 4gb RAM, Radon HD6850) should be more than able to handle the situations. The computer does get quite hot, but nothing too high (HowTos)