When you create or entry into a ready-made world, in the log appears this error:

http://pastebin.com/BgZj92PA

If i delete AdventureBackpack2 - this error disappears.

adventurebackpack-1.7.10-0.8c

this is a massive issue!

The amount of trash this error generates makes log files grow insanely and clients crashing with out of memory. This error will happen every single time you open an inventory!!