Error using horzcat - Seed-based Functional Connectivity

Hello,

I just started to do my first resting-state analysis using the REST/DPARSF toolbox. I want to do a seed based functional connectivity analysis. But unfortunatley the an error occurs after I've extracted the ROI time course (for details see below). I am using a Mac OS X (Version 10.8.2), Matlab 2012b, SPM8, REST (Version 1.8), DPARSF 2.1. 
Any suggestions?

Extracting ROI time courses over, elapsed time: 10.01 seconds.