Hey Pirata, I totally get your pain. I was in your boat. But today, I finally figured out a solution. At least it worked for me.

Use RivaTuner 2.0 final. Go to Driver Setting, Customize, System Settings. I'm sure you know how to do this part already.

Here's the tricky part. Toggle the drop down to 2D. Set your underclock setting. Say gpu350/ram750. Hit Test. Hit Apply. Now toggle the drop down to 3D. Again set it to your underclock settings, 350/750. Test, Apply. Now save! Call it underclock or whatever. Then hit OK to exit the panel.

Repeat the steps described in the above 2 paragraphs, except this time, set your OVERCLOCK settings. And call it something else, say overclock.

Now go ahead and create launchers for both, then create desktop shortcuts. If done successfully, you will be able to manually toggle your underclock and overclock settings, gpu AND ram!

I personally prefer the manual method, since Rivatuner or the driver or whatever seems to detect random programs and crap as 3D, and thus automatically apply the 3D settings even though I'm surfing the web. I've gotten the auto 2D/3D toggle to set the oc/uc speeds correctly before, but as I said, I hate it when it keeps OC'ing my card on desktop. Hope this helps!