afni.nimh.nih.gov

Jen,
I had a similar problem with my dataset, and Ziad Saad told me to run 3drefit and use the -markers options. Like this (let's call my dataset elvis.hdr):

3drefit -markers elvis.hdr

Now if you launch afni and go to "Define Markers", the "Allow edits" button will become highlighted.

Good luck,
Peggy