256x Texture pack not loading

So today i downloaded sphax 256x and installed it in resource packs folder. but when i load the texture pack it says out of memory. I ran sphax 128 just fine but i want to use 256 badly I have optifine d3 ultra and ive allocated 2 gbs of ram to minecraft!
i have a Intel core 2 Duo CPU, 3.00 GHz, 4 gb of ram, and a x86 proccesor