Hi Madbat,
There's a thread in the DAZ Carrara forums about the sunbeams; they're tricky to set up-it's all done in the Realistic Sky editor. I did get 'em to work eventually...
I'm getting the same stability issues on a cheap PC and on my badass workstation. (I really only spent $800 on it!)
I'm surprised how fast C8 renders on both machines, but the 64Bit version definitely has the edge.
I'm looking forward to the next beta release with the Bullet Physics Engine for soft/rigid dynamics!