Hi Jon,

What is the actual error message that you see on the screen (the
"unexpected grid size change" message)?

Also, what is the actual command line that does not seem to finish
when you use 3dfractionize?

It sounds like you may be using warp-on-demand for resampling.
If that is the case, you will need to make a resampled dataset;
warp-on-demand does not actually create the necessary, resampled
dataset.

If you want to draw on the grid spacing of the functional dataset,
you could use 3dresample to warp the anat:

3dresample -rmode NN -inset anat+orig -master func+orig -prefix anat_resam

Or you could switch the -inset and -master to resample to the func
dataset. The "nearest neighbor" resampling mode on the command
line isn't too important if you resample the anatomy. But if you
resample a mask dataset, you will probably want it to preserve the
integral mask values.

If I'm babbling about nothing since you already have a resampled
dataset, please supply the details of how it was created.

Thanks,

- rick