I can't be sure but it may have to do with rendering itemframes. See crash report below.
What I expected to happen was...:
To log into the server
What actually happened was...:
I logged into the world. The game momentarily rendered and suddenly the game crashed.
Environment
OS: Windows 8 (ver 6.2, arch x86)
Java: 1.7.0_55 (by Oracle Corporation)
Launcher: Minecraft Launcher 1.3.11 (bootstrap 5)
Minecraft: 14w18a (updated Wed Apr 30 11:25:35 BST 2014)
Duplicate of MC-54008