Need Some Help With Overclocking GPU's - Experiencing Some Problems

Hello,
i've been testing out some of my graphics cards in my old system before i put my new one together.

I've been doing some Crysis Warhead benchmarks with all cards and saving the results.

Now i want to try my hand at overclocking each of the cards and then benching them and comparing the results.

So far I've only been trying to overclock two of my GTX275's using Rivatuner, Evga Prescision and Furmark for stability testing.

However, it seems I've hit a slight snag, as best i can figure Rivatuner is not detecting my cards clock, shader and memory settings.

Leaving that aside for a moment, when i open up Evga, there is no bar for changing my shader clock settings, this was also the case in Riva tuner, but in Evga, my core clock and memory settings are available for adjustment.

Core clock, shader clock and memory speed are all displayed in the 3 bars beneath the GPU temperature, only Core and memory are available for alteration, however they do not seem able to be altered as when i alter a measurement and press apply, it resets to it's default.

Leaving Rivatuner aside for the moment, does anyone know why i may be experiencing these problems in Evga precision?

To makes things more simple I've uninstalled Rivatuner for now.

I've just tested a GTX 280 and it's the same deal, can't adjust the shader clock, can adjust the core and memory, but when i hit apply, they reset to their original value.

In case anyone is wondering i am adjusting by only very small increments and have tried increments on varying sizes.

Click on 'Link' to enable independent core/shader OCing in Precision.

I also have the GTX280. Exactly what clocks are you at and what clocks are you trying?

Run a small window (640x480 or so) of FURMARK to see 3D clocks while testing out different speeds. If not he card may go back into 2D mode.