CK won't let me make a script.

Hi, guys.

When I try to add a new script to a Quest or Magic Effect, the CK won't let me do it. I've done it before hundreds of times but I just got a new PC so it's a fresh install.

When I try to add an extends: activemagiceffect it says "The extends script does not exist, pleasep ick one that does" even though I can see the thing in the folder, and when I try to just make a blank new script, it says "unable to create the new script file".

I do have the source folder extracted and all that, abd my whole Steam folder is in C:

Skyrim folder is pristine. Nothing in it that's not vanilla, all mod materials are in MO, which I'm not using for this.

Does anyone have any idea what I might be doing wrong?

Thanks.