Cool, thanks. Managed to get it to work, though it seems to be running worse with Optifine for some reason. I'll figure out how to reduce this lag eventually. I'm not concerned for the graphics at this point, just want my few mods and as little lag as my laptop will allow.

So optifine for 1.2.4/1.2.5 has been released. Ladders and vines are now climbable, BTW ropes are not. I would suspect that it is the forge compatibility support optifine has introduced in this version that breaks them. I'm not a coder so honestly that would just be speculation on my part. I've yet...