Sorry for the late reply
For the version thing, no. I downloaded NASM on this version and I'm not even sure how to change the version. The strangest thing is that including the libraries in the .asm file works just fine, but if I'm including one header file into another header (with relative path), it gives the fatal error.
[EDIT Unrelated, but another issue is that when i do %endrep NASM thinks I'm trying to do modulus on a label. Maybe I half-downloaded it or something like that, 'cause its really scuffed right now