I've made a crash report in the galacticraft tracker, but since radfast said this problem might be on BoP's end, I'll leave this here too :)

Original Issue: micdoodle8/Galacticraft#1094
When right clicking the terraformer, the game crashes with a ArrayIndexOutOfBoundsException. This only happens with Biomes o' Plenty installed.

Versions used:
BiomesOPlenty-1.7.10-2.1.0.993-universal
GalacticraftCore-BETA-1.7-3.0.4.209
Galacticraft-Planets-BETA-1.7-3.0.4.209
MicdoodleCore-BETA-1.7-3.0.4.209
MinecraftForge 1208

Crash Report
http://pastebin.com/aRxVPZz4

@Adubbz close. Fixed by #587

I can confirm this crash, using the same versions of the mods.
There's quite some good leads to how the problem might be solved over at the original Galacticraft issue thread though, with a direct link to the GC code that is involved in the crash, so I guess that this bug might be relatively quick to fix.