I'm running on an original B, but the site mentions nothing about the split - so maybe it only works on the 512mb models (I really wish they had changed the name, though the site says "A Raspberry Pi mini-computer" is required, and I doubt it works on the A, so they don't seem to be explicit any way).
Make sure you are running 0.1.27
As for the black screen, currently a known issue that seems to occur before caching is done.
I appreciate the (presumable) desire to make it easy for people to burn the image onto an SD card, but when I see this:
> Please re-run this script with root privileges, i.e. 'sudo ./getrasplex.py'
without any kind of explanation, or justification, just a "do this!" instruction, the answer is "NO".
We have plans to have a single, GUI installer, but only have so much man power.
Again, still in Alpha. The project is only about 1 month old.
I have a better solution for caching being cooked up but it's at least a few weeks away.