"Saving chunks" + white screen after numerous attempts

[Daga]

Title: "Saving chunks" + white screen after numerous attempts

Version: 3.0.3/3.0.4

OS: Windows 7 Ultimate 64-bit

Java Version: 1.7.0_05-b06

Description of Problem:

Whenever I do anything, after a short while I'll get a message saying Saving chunks and then it'll turn into a white screen, crashing the game.

This keeps happening, even after removing Tekkit about 4 times and clearing cache.

I do alter my modpack slightly, cause I use Optifine Multi-Core version, but besides that I don't change anything.

I also use the Sphax 64x texturepack.

Error Messages:

Saving chunks

Error Log:

http://pastebin.com/fmHSZssy

[Torezu]

Try reinstalling Java. Make sure you get 64-bit, of course.