My X1800 GTO is giving me a headache, it was running great at 600/600, but then it suddenly started locking up during 3d applications. I thought I was running out of power, but after throwing an Antec Smart Power 2.0 500W PD in, it is still doing this. It's the core that keeps locking up after I go over 550, and the higher the voltage, the quicker it locks up. I have gotten it fairly stable at 1.175 with 1.90 I/O voltages, but it still locks up after about 5 minutes of a 3d App. The memory is just fine, I can go right up to 650 without issues. Does anyone have a clue as to what I can do about this? Thanks in advance.