Relevant bit from end of log:
Spoiler
Crash Report ----
// Surprise! Haha. Well, this is awkward.
Time : 2/8/15 1:40 PM
Description: Registering texture
net.minecraft.client.renderer.StitcherException: Unable to fit: extratrees atterns/letterb3.1 - size: 16x16 - Maybe try a lowerresolution resourcepack?
at net.minecraft.client.renderer.texture.Stitcher.func_94305_f(SourceFile:56)
at net.minecraft.client.renderer.texture.TextureMap.func_110571_b(TextureMap.java:242)
at net.minecraft.client.renderer.texture.TextureMap.func_110551_a(TextureMap.java:90)
at net.minecraft.client.renderer.texture.TextureManager.func_110579_a(SourceFile:72)
at net.minecraft.client.renderer.texture.TextureManager.func_110580_a(SourceFile:61)
at net.minecraft.client.renderer.texture.TextureManager.func_130088_a(SourceFile:52)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:537)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:867)
at net.minecraft.client.main.Main.main(SourceFile:148)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method )
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method .invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------
-- Head --
Stacktrace:
at net.minecraft.client.renderer.texture.Stitcher.func_94305_f(SourceFile:56)
at net.minecraft.client.renderer.texture.TextureMap.func_110571_b(TextureMap.java:242)
at net.minecraft.client.renderer.texture.TextureMap.func_110551_a(TextureMap.java:90)
-- Resource location being registered --
Details:
Resource location: minecraft:textures/atlas/blocks.png
Texture object class: net.minecraft.client.renderer.texture.TextureMap
Stacktrace:
at net.minecraft.client.renderer.texture.TextureManager.func_110579_a(SourceFile:72)
at net.minecraft.client.renderer.texture.TextureManager.func_110580_a(SourceFile:61)
at net.minecraft.client.renderer.texture.TextureManager.func_130088_a(SourceFile:52)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:537)
-- Initialization --
Details:
Stacktrace:
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:867)
at net.minecraft.client.main.Main.main(SourceFile:148)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method )
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method .invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
-- System Details --
Details:
Minecraft Version: 1.7.10
Operating System : Windows Vista (amd64) version 6.0
Java Version: 1.8.0_31, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 153584032 bytes (146 MB) / 737079296 bytes (702 MB) up to 4260102144 bytes (4062 MB)
I guess the question is, are you using any resource packs?