Too Much?

[GuardianAsher]

I have an ASUS nVidia GeForce 6800XT. Stock clocks on this thing are 300MHz Core, and 700MHz RAM. I'm a performance nut, so of course that's not enough. I've managed to get this thing to 415MHz core and 875MHz memory, but any more and it either doesn't pass the driver tests in RivaTuner, or the system just freezes. Have I overclocked this thing just a tad bit too much? The temps stay at a constant 50C for GPU and 49C for RAM on the overclock, compared to 48C GPU and 45C on RAM. It was higher before I rewired my case. Any info would be appreciated. I'm new to the overclock scene.