The FTB Forum is now read-only, and is here as an archive.
To participate in our community discussions, please join our Discord! https://ftb.team/discord
In your configs, what is in biomesoplenty terraingen.cfg? if worse comes to worse get in your world folder and delete nether unless you have stuff you need down there. Looks like its got issues genning terrain.
Edit, also what are your arguments in the ServerStart.sh?