Delia,
I have the same issue and have yet to get any answer. I spoke with Red Giant and they essentially said it is a Premier issue. I have had trouble rendering simple 3 min videos using Premier with or without Red Giant. The only answer I get from Adobe is that they are working on it. If, you look through the different threads you will find many rendering issue posts, usually with the same theme, crashing on export or just going dead at random time frames. The only option that has saved me so far is closing the software, going into processes and closing all adobe links and then reopening Premiere and trying another render. That sometimes works, but no guarantee. You might want to check in your project settings to see how you are rendering (CUDA or Mercury Playback) Red Giant software really only works on CUDA. Good luck!