Since the 1.9 update, when I select certain texture packs (with experimental features turned on) and then try to load a world, old or new, the game will hang for a bit on the loading screen and then crash before loading the world.

I have a lot of texture packs, but the ones I noticed this problem on so far are:

-ChromaHills HD

-VanillaBDcraft

-ZigZag

However, I have just discovered that I can use ChromaHills HD texture pack on an already loaded world only if I copy the world and use the pack on the copy, but it needs to be on a fresh copy that's never been loaded any other texture pack before (edit: I also can't rename that copy to anything else or it once again crashes). The other glitched texture packs do not successfully load with this workaround.

Edit #2: Further testing has shown that if I don't turn experimental features on, I can initially load a new world with ChromaHills HD on, but an exit and reload of that same world causes the game to crash again before it loads.