Casy (atys)
Did you run other games and/or 3D Benchmarks successfully for more than 45min? Usually this kind of problem is due to faulty hardware (possibly combined with driver issues). You can also use a temperature monitor for your graphics card to monitor GPU core temperature. You are describing a very likely symptom of excess heat. A quick google also shows some issues with badly seated heatsinks on 7770s.
This is the only game It lock up with. I've played hours on high RFPS games and even run bitminter while not using my computer. It's NOT a heat issue or faulty GPU.