Monster severe lag and crash

[Blitzkrieg78]

When I play monster, I get really bad lag. Like 1-4 FPS lag. I know its not my computer specs because my brother runs it at 40 FPS on the exact same computer. I have tried re-downloading Java several times and force updating. Also I have tried optifine, but that just immediately closes the game when it starts (no crash report). I have tried the JVM perimeters and optifine light. Optifine light doesn't crash the game but it doesnt really help with my FPS lag.

PLEASE HELP ME!!!!

P.S. Just noticed that console is spamming this (sorry for the screen spam):
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] 1286: Invalid framebuffer operation
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] ########## GL ERROR ##########
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] @ Post render
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] 1286: Invalid framebuffer operation
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] ########## GL ERROR ##########
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] @ Post render
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] 1286: Invalid framebuffer operation
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] ########## GL ERROR ##########
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] @ Post render
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] 1286: Invalid framebuffer operation
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] ########## GL ERROR ##########
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] @ Post render
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] 1286: Invalid framebuffer operation
2014-01-20 09:19:14 [SEVERE] [Minecraft-Client] ########## GL ERROR ##########

 

[JamiePhonic]

i believe this error is related to mapwriter's unverground option. press u on your keyboard while in game and see if it stops

 

[Blitzkrieg78]

That didn't help any :/
Is there anything else besides optifine that could help my FPS?

I REALLY NEED SOME HELP!!!!!