OS3.9 datatypes use WarpOS if it is installed. So if it hangs on loading the backdrop, then something is wrong with your PPC.
Check if the PPC fan works and that it's not getting too hot.
I'd also test it with the G-Rex disconnected.
How did you install WarpOS ? All archives available for download are updates only. You first have to install "PPC support" using the OS3.9 installer, then you can install the updates.
Which firmware does your CSPPC have ? Did you make an update for the G-Rex ?
Did you install the 68060.library matching the CSPPC firmware version ?
and this is with a fresh 3.9 installation, bb1+bb2, and cgx4
You should install everything chronolocically. First OS3.9 + 68060 libs, then WarpOS, then BB1. Now PCI libs, CGX4 + update and BB2 as the last.
Bye,
Thomas