Multiboxing D3 - Lag issues

Hey everyone.

After a fresh reinstall of windows+everything, im having trouble. My GPU is bottlenecking me!

I used to be able to 3box + stream in 720p60fps without any trouble at all be fore the reinstall, but now is a different story. My GPU usage, when reaching 100%, makes the game run like its in slowmotion - normal resource lacking issue i suppose.
But why didnt this happen before? Even when I was streaming for 12 hours out end, I mean - something happened. Any ideas on how to fix this?

Pc Specs:

i7 2600
16gb corsair
gtx570 1.2gb
win 7

Usage:
CPU: 70-100%
GPU: 90-100%

[lax]

You probably had different graphics settings, or a different version of your graphics driver. If you didn't specifically install an NVIDIA driver after reinstalling Windows, you should go do that now.

Otherwise, I would be dropping some graphics settings as suggested under http://isboxer.com/wiki/HOWTO:Tweak_your_framerate#In-game_configuration