Blender 2.65 Rev54568 Keeps crashing in Rendered view

I keep trying to make changes to my materials while I am in “Rendered View” of blender. But it keeps crashing. Do you guys have any idea what could be causing it?

I have samples to 10(Both Rendered & Preview)
I run it with CUDA GFX Card render (gforce 660)

Try the latest build, it has also material preview > http://download.blender.org/release/Blender2.66/

Cheers, mib.