relevant logs: http://pastebin.com/qSGah5N6

enderIO 2.3.0.421 beta
galacticraft 3.0.12.375

game locked up then crashed, when placing a teir 1 conduit, on the ceiling, near a GC arc lamp.

also posted on micdoodle8/Galacticraft#2042

link #2835

Fixed in Galacticraft.

Hint for others: Check if invalidate() calls super().