Hmmm, I wonder if this is an issue of Mac doing things differently than LInux and effectively passing along the wrong information (sometimes on Macs, keypresses work differently, oddly enough).

From a previous post having this issue:
[afni.nimh.nih.gov]
...updating the binaries helped (that person didn't report the original AFNI version, unfortunately). What version of AFNI do you have?

This person resolved a similar issue:
[afni.nimh.nih.gov]
.... by using "shift+r" to start recording a video, but just making the video be 1 frame, and saving it as an image.... I hope there is a better solution, but I am not sure.

--pt