afni.nimh.nih.gov

Hmm, I took your command and ran it on the FATCAT Demo set (changing file names appropriately), and it ran without a problem.

My first question would be what version of AFNI is being used? -> what is the output of:
$ afni -ver

But my guess is that there may be something in the data sets themselves. Would you want to send me a tarball of the data in question (dti* and 1.nii.gz), and I can try to investigate that? (If you click on my name, my email is in the User Profile.)

--pt