Just made an account to comment here. I'm using version 1.0.2, and have had zero issues in the 2 months or so i've been playing through regrowth. today however, after switching out of my world to test a mob grinder in a test world, I came back to only be able to boot up the world for like half a second, then it drops out and gives me the error "a fatal error has occurred, this connection is terminated" and sends me to the multiplayer tab. Only thing is, is that im playing in an offline, SSP world. I'm running Mac OSX 10.11.1 and I've done no updates to the launcher, java, or anything really. I don't have a firewall enabled, nor do I have antivirus active.
The test world boots up fine, as does any other world I make. I tried reinstalling a clean copy of the modpack, but nothing changed. There's no crash logs, as it didn't crash, but here's the log from the console window (This is a fresh account, so if the link doesnt show it's probably because the mods have to approve it first, sorry for the inconvenience).
https://pastebin.com/n2Cd5GjK
If anyone knows the problem/how to fix it that would be a big help. I've had issues with agricraft causing the instance to crash, requiring MCedit to clear out the agricraft stuff, so if that the error again, i'll happily clear it out again.