Why is Minecraft dropping frames so bad?

I have recently built my first gaming PC and have been playing Minecraft with ShaderModCore, Forge, OptiFine, and SEUS shader mod v10 installed. I can't for the life of me figure out why I was playing stable at 46fps for several days, now today to find it is stuck at 13-16fps. What the heck is going on? I reinstalled Minecraft, reinstalled Java, and checked for a video card update to no avail. I checked my temperature which are: (using SpeedFan):
GPU: 65C
Temp1: 42C
Temp2: 40C
Temp3: 51C
HD0: 34C
So, I need to know why the fps has dropped so drastically so quickly.

Added (1). Those temperature are while playing Minecraft btw.

Guest

Looking in the Steam forum, a member with a computer using the on-board Realtek Audio, disabled the Realtek Digital Output playback device and solved his frame rate issues.

Right click the volume icon -> Playback Devices -> scroll down and select the Digital Output -> select Properties -> On the Device usage field select "Don't use this device (disable)" -> click Ok, etc.

It could be some other driver, even a recent antivirus signature update.

Charlie Tuna

There's lots of things that cause it. Try lowering your graphic settings a bit also every once and a while search up %temp% and delete everything in it. If that dosen't work do this: http://howikis.com/Increase_Computer_Speed_Using_your_Notepad and follow the page. Also try downloading razer game booster it helps ALOT. If you do these you should be in the 50's frame rate like me if you gave at least 6 GB of ram
heres the download for razer game booster: http://www.razerzone.com/...amebooster

ben