Yeah, I think the problem is more wear 'n tear then an overclock issue. When my system was new almost 4 years ago, it did everything I wanted and then some with barely any overclock. I get horizontal lines in my tv screen every once in a while, a lot less now then when I tried to fix it. I'm due for a brand new build but can't afford it right now, parts I use for my builds end up between $1500-$2000 and my new build I shouldn't even have to overclock.
Believe it or not, it could be the HDMI cable. My vid card has 2 DVI ports so I need a converter to plug my pc into my tv (HDMI). Checked it out and it seemed awful loose fitting into the DVI to HDMI connector. Never had a problem before going back years so I am going to either dig up or buy a replacement HDMI cable and see.