afni.nimh.nih.gov

Changing the datasets underneath afni is not
advisable. If you are not viewing (underlay
or overlay) the changed datasets, it might be
enough to do:

Define Datamode -> Misc -> Purge Memory

and then re-select the datasets. But if the
.HEAD information has changed (orientation,
voxel size, etc), it will probably still be bad.

- rick