That line is part of the internals of parfor, and is where the desktop MATLAB client session sits waiting for results coming back from your workers. I would recommend perhaps adding disp statements to your parfor loop to help you work out where your workers are getting up to. Or perhaps modify your code so that you force your parfor loop to run on your desktop MATLAB by doing this:
parfor (idx = 1:N, 0) % <-- the 0 means "run locally"
... % do stuff
end
