Just noticed that my inverted white lanterns, that i placed some time ago, turns invisible and untargetable, like they are not exist. But i can't place any block on their place, and when i try to break block, which lantern is connected, my client crashs.

Crash Report: http://pastebin.com/wJrK1Rjq

This is a known issue with Forge Multipart (Chicken-Bones/ForgeMultipart#139). I am unsure whether it was resolved but when the big update to 1.7.2 is released we shall see whether it's fixed. I'm unsure of a fix in the meantime though.