YouBot looses EtherCAT connection upon starting sound_play

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Hi,

I am using ROS Indigo on Ubuntu 14.04 for controlling a Kuka youBot. The robot, using the available drivers, typically works okay. However, upon starting sound_play (a package for converting text-to-speech), through the following command,

rosrun sound_play say.py 'Hello World'

the robot computer looses connection to the robot hardware and the driver stops responding (similar to the error reported here)!

I am wondering what might be the reason for this behavior, and the steps that I could take to resolve this issue.