With fastcraft:
===========
"Client thread" Id=1 RUNNABLE
        at org.lwjgl.opengl.GL11.nglTexSubImage2D(Native Method)
        at org.lwjgl.opengl.GL11.glTexSubImage2D(GL11.java:2984)
        at net.minecraft.client.renderer.texture.TextureUtil.func_147947_a(TextureUtil.java:187)
        at net.minecraft.client.renderer.texture.TextureUtil.func_147955_a(TextureUtil.java:170)
        at fastcraft.a.j.a(F:566)
        at fastcraft.Hooks.i(F:85)
        at net.minecraft.client.renderer.texture.TextureUtil.func_147955_a(TextureUtil.java)
        at net.minecraft.client.renderer.texture.TextureMap.func_110571_b(TextureMap.java:283)
        ...

Without fastcraft:
=============

"Client thread" Id=1 RUNNABLE
        at org.lwjgl.opengl.GL11.nglTexSubImage2D(Native Method)
        at org.lwjgl.opengl.GL11.glTexSubImage2D(GL11.java:2984)
        at net.minecraft.client.renderer.texture.TextureUtil.func_147947_a(TextureUtil.java:187)
        at net.minecraft.client.renderer.texture.TextureUtil.func_147955_a(TextureUtil.java:170)
        at net.minecraft.client.renderer.texture.TextureMap.func_110571_b(TextureMap.java:283)
        at net.minecraft.client.renderer.texture.TextureMap.func_110551_a(TextureMap.java:97)
        at net.minecraft.client.renderer.texture.TextureManager.func_110579_a(TextureManager.java:89)
        at net.minecraft.client.renderer.texture.TextureManager.func_110549_a(TextureManager.java:172)
        ...
        ...