It does sound like MCW_file_expand() is failing to find anything when it tries to expand (say) the string "./*" to get a list of all the files in the current directory -- which is what it will do when you start afni with no arguments.
How to fix this is less than clear, since I've never seen this function fail before. MCW_file_expand() is basically a wrapper for the csh filename expansion function. Perhaps I can come up with a workaround, but it will be hard to test here since I don't have your setup.
Does the command
echo `ls ./*`
give a directory listing?