I have no trouble launching the Creation Kit or loading plugins, but I can't use it because it freezes forever and says "not responding" every time I want to change a model.

I'd like to make a mod for Skyrim that replaces vanilla weapons and, whenever I open, for example, IronSword, and, in Art and Sound, I click on Edit (model), the program freezes.

I've tried giving it time, but, after 10 minutes, it was still not responding.

I've searched for this issue but it seems nobody else has ever gotten it. I would appreciate some help. Thanks!

Your computer might not be powerful enough to handle the Creation Kit...

My system specs:

i5 3570k @ 4.0GHz

16Gb DDR3 @ 1600

2x 270x 2Gb on CrossFire

Crucial M500 240Gb (SSD)

Windows 8.1 x64

EDIT: The program works well overall, but it always freezes when I click on that - a new window called "Model Data" appears but after a few seconds it also says "not responding" (like whenever a program gets stuck in Windows). My guess is what should open is a folder browser (to select the file), and I have no idea why the program dies there.

Your nif is corrupt, compare it with a similar vanilla nif block by block in Nifscope.

I always use http://www.nexusmods.com/skyrim/mods/12801/? and use maximum profile, resizing down textures to 1024. Might that be the reason - that I no longer have the original files and those are the only ones that work for CK?

Bad or missing textures shouldn't necessarily cause the CK to crash (most likely you will have a white or purple nif), a bad nif will most definitely cause it to crash.