Weird Lag

[TinkerFox]

So sorry if this is in the wrong place in the forums...

Today i downloaded FTB Direwolf20 for mine craft 1.6.4, i have lots of experience playing the othe mod packs and my computer is pretty good. I played the previous version of Drirewolf20 (1.5.2) and i played with high settings and render distance medium. When i play this new mod pack, I have no lag AT ALL for about 20 mins then all of a sudden there is massive lag and i have to force quit to exit the launcher because it is non responsive. I don't understand why there is no lag AT ALL, perfect FPS then it just dies and crashes and i cannot play. I also want to add that i tried to add optifine but half way through start up the client crashes
Thanks For Any help!

 

[Radiant9d]

1.6.4 had an issue with the extended zombie pathfinding causing LOTS of lag when you are close enough to load a village. Perhaps this is the issue? Just a guess.

 

[TinkerFox]

So i updated my java to the newest version (version 7) and now i don't have the lag problem but my friend who was having the same problem with an even better computer has also updated his java and he still gets the weird lag.

 

[Ashzification]

Your friend can post a thread then. Having a middle man always makes things more confusing.