http://pastebin.com/hXLRqU1G it happens randomly in the world. This caused by Better Foliage as skyboy (MFR dev) said. Tested on Forge 1286, latest MFR and Better Foliage.
Another crash but know something with Natura: http://pastebin.com/YsL5u1ap

Thanks for looking. It might be not BetterFoliage and not MFR. I dunno why they both mentioned in log. I'll continue investigation.

Seems to be some strange case I've not considered.
I've added some code in version 1.0.4 to stop crashing and log the error. Look for messages like "ArrayIndexOutOfBounds when rendering block" in your log and/or graphical glitches to see if the problem persists.
Closing for now.