Board Thread:LotR Mod Technical Support/@comment-25330335-20150131155904/@comment-27172148-20151108210332

So all of the things I said about Java JVM parameters and memory apply to your situation as well but, more likely something is messed up and the ultimate (and easy) solution is just a clean slate.

By this I mean renaming your default hidden Minecraft application folder to force Minceraft to create a fresh one. Note: this is not the same as merely creating a new Game Directory in the Java launcher. By default, they are the same (unless you ever changed it), but JUST changing/making a new Game Directory in your usually won't help.

Allowing for a brand new Minecraft application folder 90% of the time is the only way to clear this problem up.

So on a Mac, this folder is: /Users/ /Library/Application Support/minecraft. The/easiest/cheesiest way to get to this hidden folder on any system, Mac, PC, or Linux is to launch minecraft, bring up the Resource Pack menu, not be in full screen, click the Open Resource Pack folder, and this will take you directly two levels below where you need to me. Just navigate up a couple levels and you'll see the hidden minceraft (or .minecraft) folder,.

It'd grap a copy of your servers.dat file (saved server addresses), rename that /minecraft folder, install minecraft, set your profile to 1.7.10 (plain vanilla), create a new single player world, make sure that works, then install Forge 1.7.10 client (build 1230 or later), select your 1.7.10-Forge profile in your launch, and if you have the LOTR Mod still in the proper folder, again now try to create a new single player world. And 99% chance you'll be all good now.