Install this mod (drop it into your mods folder). Then, whenever you start Minecraft, another small window will open which has a button labled Create Thread Dump
. Press that button whenever it is frozen (not slightly before or after, it has to be while it is frozen). Copy the thread dump from the text area above the button to some pastebin site and note down the link. Repeat ~5 times, then post the links here.
Please also list all installed mods with their respective versions (best to directly pastebin the fml-client-latest.log
file inside the log folder inside your .minecraft folder which will contain that list).