Perfect! Running FEKO in sequential mode produced a single .mat file that I was able to read using the mat2ascii utility. Your help fixed my problem in a jiffy.
If it helps anyone else, I managed to find a workaround that I used before this fix. I needed the complete NxN Y-parameter matrix of my antenna. But with one driving port (call it port p), the FEKO .out file only gives me one row/column of the Y-parameter matrix Y(:,p) = Y(p,:). So what I did was to create N ports on the structure (one on every segment of interest). I then ran the mesher once and adjusted its settings so that the segments were centered on my ports. (This worked except for the ports at the very tips of the antenna). I then ran N simulations, enabling only one port at a time. After each simulation, I extracted the single row/column of the Y-parameter matrix from the .out file, until I had the complete NxN matrix. Admittedly not very elegant, but it worked. Now that the mat2ascii utility is working, I will use that instead.
Thanks Jif