A couple days ago, I began to install mods on my minecraft.jar. I had Optifine, ModLoader, and HDSkins running. Today I tried to play a little Skygrid (Link Here: http://www.planetminecraft.com/project/skygrid-survival-map/) With no other windows open. Basically the blocks would load up but then, about 3-5 seconds later, Minecraft would crash. One of the crash reports is attached. I replaced the .jar with an un-modded verson of Nodus (a 'hacked' client. The same thing happened. I started up a new world and it was only lagging a little until I began using the 256x version of Sphax. Once I changed texture packs, Minecraft froze up as usual and crashed. This is understandable, as I have only allocated 7GB of ram to java. But why is it that when using default texture pack, and even an 8x texture pack, Minecraft still crashes on Skygrid. I have not yet tested the other worlds. If I need to get more ram or a better Processer (i3) or something, I am willing to. I was going to get a parts upgrade soon anyway.

Side Notes:
All my other games(stuff like: Skyrim, Guild Wars 2, Portal, Tekkit) run fairly smoothly.
Also, I force updated minecraft and had the same issue.