Hi Nick,
Thank you so much for your response. Turns out that the XQuartz had updated to 2.7.6, I've reinstalled 2.7.5 and it is working!
Finally I can finish this study!
Best wishes,
Gill
_____________________
Gillian Cooke, Ph.D.
Postdoctoral Research Associate
Lifelong Brain & Cognition Lab
Beckman Institute
University of Illinois, Urbana