Answers to questions:
1) Yes - either the image/BRIK data, or a complete (single TR) data set.
2) I think what I saw was the function trying to access the registered data set before that data set had the reference volume to which others were being registered. If I just have it try to write the individual (unregistered) volume, I don't get the error message I initially thought would have been a clue. But I still don't see anything being written out to disk ...
3) The location I posted in my first post seemed to be the logical place, from what I could glean in the code ... I see the print message to stdout printed just before the EDIT_dset_items and DSET_overwrite function calls, but I don't get anything on disk ...
4) Hey - I'm just the hired help here. I'm not working in MATLAB. I'm just trying to help the person that has to ...
I can send along either my modified source code, or a diff between mine and the downloaded source (from last week), if that might be helpful ...
vinai