[ubuntu] Blank Screen

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http://ubuntuforums.org – I have Ubuntu 12.04 64 bit installed on my desktop.I can boot up with no problem. After a few minutes the screen goes blank for one or two seconds then back to normal. This happens the entire time I have my desktop running. I HAD Zorin 6 installed and had the same problem.I also tried Mint 13 with the same results. I thought switching OS's would fix the screen blanking but it did not. Any ideas? (Hardware)