Hi,
Thank you for sending the scene. I have rendered it in v5 and it is working fine for me i.e. no fireflies.
I will suggest doing the following, in this order:
1) Reset your render settings (Render setup -> Scene -> Reset settings)
2) Reset LightMix completely
3) You have many empty objects etc in the scene as well as some unsupported materials. I would suggest running something like prune scene or SiNi forensic to remove these.
4) Reset your licensing files, I know this sounds strange but in some cases it does work. To do this navigate to: "C:\Users\USERNAME\AppData\Local\CoronaRenderer" and delete everything in this folder.
Thanks,
Rowan