Parallel pool shut down due to error?

I'm trying to execute a code using 12 parallel workers with parfor in Matlab-r2014b. I am allowed to do it since the machine I'm using has 12 cores.

However when I start running the code, after 10-15 minutes, the symbol on the bottom left of the Matlab screen [next to the word "Busy"] (which is usually a blue or green rectangle when parfor is properly working) becomes grey with a yellow triangle. If I pass the mouse over it I get a message saying "Parallel pool shut down due to error". The Matlab command window does not report any error and the code keeps working I guess using just one worker.

Any idea of the possible causes of the message?

[Sean de Wolski]

Minimal working example of the code?

[Edric Ellis]

If the pool shut down in this way, that usually indicates a crash on one of the workers.