Quote from JonnyBrando
Hmm what video card and driver are you running right now? I can't recall if we've gone over this part before?
Also, what shaderpack are you using?
You might post the logs (%appdata%\.minecraft\logs) of when it was working, and when it wasn't... It could be a shaderpack error..
Have you tried updating your video drivers like I recommended?
I assume it runs without Optifine and GLSL?
Download and install Optifine, still working? Then add GLSL..
Can you go to %appdata%\.minecraft\logs folder and post your fml-client-latest.log?
Here it is : http://pastebin.com/jA1p7LyP