I am almost 100% certain that this crash is thrown when nodes spawn or tick. This crash occurs during new world generation in any biome type and was tested with the mod removed and before.

http://pastebin.com/ZRhnM3Rd

If I had a wild guess it would be something to do with this class and the use of runnable: https://github.com/SilentChaos512/SilentGems/blob/e55c6bc583ccc799532fba8e30868541166ee3e4/common/net/silentchaos512/gems/client/handler/ClientTickHandler.java

Hmm. After several more hours of testing I got another crash out of the blue. It appears that this is not due to your mod. Time to keep hunting, my apologies!