Version: 2.5.0 What is the bug: First off the error log: http://pastebin.com/uYKhwUyU Description: Placing a transfer pipe (from extra utilities) at depth level 0 causes an ArrayIndexOutOfBoundsException error that crashes the game and prevents clients from connecting to the world (both SP and MP). Mod & Version: Extra Utilities? Paste.feed-the-beast.com log: http://pastebin.com/uYKhwUyU Can it be repeated: Yes I've repeated it in SP after discovery in MP. From new world, build down to Depth level 0. Place a transfer pipe at depth level 0. Crash upon placing pipe. Placement of Pipe at depth level 1+ won't crash it. Known Fix: Deleting the block via MCEdit will fix the problem but will not prevent it from happening again. Best to avoid building pipes that low in the world.