TV screen blanking out at 60 hertz.?

[Tsmith]

I have been running my computer on my TV for around 6 months now, I initially had it set up with an HDMI going straight to the TV. When I was doing this my TV screen would be black and freeze on some of the higher resolutions (it is a 1080p TV). Last weekend I bought a new amp to support HDMI and once I hooked it up the TV suddenly could support every graphics type without an issue, is looked way better in 1080p and I have been running it like that for a few days now. Today I left for around 2 hours, turned off the TV and Amp but left the computer on. When I came back I turned on the TV and amp again to see a black TV screen. Initially I though the connections were loose. However, when I managed to get a hold of the resolution window and bring it to my second monitor I discovered I was back to only running on lower resolutions. In 1080i the hertz options are 29 and 30 and they both work fine. For 1080p the options are 23, 24, 59, and 60 hertz. Before I was running on 60 hertz and working fine, now I can run the TV on 1080p with 23 or 24 hertz but not 59 or 60. You can really notice the 24 hertz even just on the desktop, it will be even worse in a game. Why has my TV stopped working randomly? I have tried rebooting, changing the color between 16 and 32, and even forcing the computer to try 50 hertz but nothing works.