Oddly enough, this didn't crash my game, just my world. I created a new Mystcraft world, placed down a linkbook stand, then started lagging. I tried placing the linkbook on the stand, but nothing happened(lag). After that, I tried opening my Alchemical Bag(Small, I think) and the game closed my world! Placed me in the multiplayer section, so I guess the Internal Server crashed but my client didn't... I'll have to check that Mystcraft world.

LOG: http://paste.ee/p/6stZN
Check line 7798 and down.
If this is just a problem because I was lagging due to world generation, feel free to ignore this, or close it.

Looks like your system was so lagged out it timed out syncing the inventory on open (which every GUI with an inventory does)

Thanks for the clarification.