I followed the NFSC dough recipe exactly (and this is not the first time I've made it) but it is really crumbly and won't stick together! Any ideas why and how I can fix?

Did you sift your flour? I know sometimes if I don't sift my flour it is more compact and makes the dough drier. Maybe you could add a little more liquid.

Definately too much flour;
I find that on some days i need more flour while at other times, i need less. It all depends on how dry or humid it is in your house at the time. Start by putting in half the flour and then add slowly until it doesn't feel sticky anymore.

add some liquid a tbsp at a time until it comes together. i live in a very dry climate and this recipe comes out dry.

I agree with the above, too much flour, I always add less flour because you use more flour when you roll it out.

I find it is usually crumbly to. I just dump it out on the counter and knead it together, make it into 2 discs and toss it into the fridge.

That's probably the best sugar cookie recipe I have found. I think if you add some milk, a half a tablespoon at a time and try to knead it in, you will be fine.
Flour is flour. It acts like it wants to.

[quote="jade8"]add some liquid a tbsp at a time until it comes together. i live in a very dry climate and this recipe comes out dry.[/quote

I'm in the same city you are! Yes, it's brutal right now and I thought the flour may be the issue. I'll use a lot less next time

I've fixed this by kneading in a little softened BUTTER untill the dough stays together. I use this recipe often and this works.