In my SSP world, I was trying to use the biome capsule/painter to change the biome of one of my bases. After using the painter, nothing happened for a while, and then suddenly I crashed to desktop. After, every time I log into the world, it crashes after 5-10 seconds of being in the world. If it helps, I was trying to convert a plains biome into a RTG Highlands biome.

I was able to replicate this, I created a new creative world, spawned in the biome tools, and tried to convert a plains into a beach biome. A minute or two after using the painter, it crashed with the same error.

Here is the error: http://openeye.openmods.info/crashes/35e992f4eb73cdf6d346a79584dba233

I have tried deleting Random Things, deleting the random thing.dat from my world, and deleting the affected chunks in MCEdit, none of which have worked.

Well if it's fixed i'll close this^^.

Presumably this doesn't happen with only Random Things installed. Could you check with which mods it happens?

I seem to have fixed the issue by updating DragonAPI to the latest version, v8e. However, I was having no problems whatsoever with v8d before using the biome painter.