@rm-rf I get the normal one for 20k after a kernel restart. But on a second run of the function I never get the correct particle arrangement if I change the particle number. For 30k I get a blank rectangle.
@halirutan I had exactly the same problem (I also wrote support, but no reply yet). Try CUDAResourcesInformation. If it gives you v8 for Mma and v4.0 for the ToolkitVersion, then you need to remove the downloaded CUDA resources somehow and re-download using v9. I don't know how to remove them though, so I removed the whole Mma config directory
hum, I just received a mail saying "you can upgrade MMA to version 9", and when I click on the link, the webpage says "Downloads for Mathematica 9 for Windows have been temporarily disabled to correct a rare but serious stability issue discovered after release"
@MikeHoneychurch Re background images (which you linked to), there are caveats. We got enough in there to support slide shows, but there are reasons we didn't expose it (yet) as a first-class feature. I'm getting hit with a lot of v9 stuff right now, and it might be a bit before I can fully comment/clarify on this, but I'll try to get to it soon.