I have the same problem...I believe it's an old issue, but also an old pain! I once had to render a starfield as a texture onto a giant dome - it looks quite acceptable, even if it feels rather...dumb.

The new update (build 272334) may solve the flickering starfield issue, but if it doesn't (which wouldn't surprise me), it seems that it is now possible to render to RPF (Z/G-buffered) again, so a starfield could be rendered as a separate pass and then composited into the scene later. Of course, you'd need a compositing app such as After Effects or Combustion...

Oh, and you're right. There's no flickering when rendering on a single machine.